To help you get started, we've collected the most common ways that yamlpath is being used within popular public projects.

YAML Path and Command-Line Tools

Along with providing a standard for defining YAML Paths, this project aims to provide generally-useful command-line tools which implement YAML Paths. These bring intuitive YAML, EYAML, JSON, and compatible data parsing and editing capabilties to the command-line. It is also a Python library for other projects to readily employ YAML Paths.

Contents

1. Introduction
2. Illustration
3. Supported YAML Path Segments
4. Installing
   1. Requirements
   2. Using pip
      1. Very Old Versions of pip or its setuptools Dependency
   3. Installing EYAML (Optional)
5. Based on ruamel.yaml
6. The Files of This Project
   1. Command-Line Tools
   2. Libraries
7. Basic Usage

   1. Basic Usage: Command-Line Tools

      1. Rotate Your EYAML Keys
      2. Get the Differences Between Two Documents
      3. Get a YAML/JSON/Compatible Value
      4. Search For YAML Paths
      5. Change a YAML/JSON/Compatible Value
      6. Merge YAML/JSON/Compatible Files
      7. Validate YAML/JSON/Compatible Documents

   2. Basic Usage: Libraries

      1. Initialize ruamel.yaml and These Helpers
      2. Searching for YAML Nodes
      3. Changing Values
      4. Merging Documents

Introduction

This project presents and utilizes YAML Paths, which are a powerful, intuitive means of identifying one or more nodes within YAML, EYAML, or compatible data structures like JSON. Both dot-notation (inspired by Hiera) and forward-slash-notation (influenced by XPath) are supported. The libraries (modules) and several command-line tool implementations are provided. With these, you can build YAML Path support right into your own application or easily use its capabilities right away from the command-line to retrieve, update, merge, validate, and scan YAML/JSON/Compatible data.

This implementation of YAML Path is a query language in addition to a node descriptor. With it, you can describe or select a single precise node or search for any number of nodes that match some criteria. Keys, values, elements, anchors, and aliases can all be searched at any number of levels within the data structure using the same query. Collectors can also be used to gather and further select from otherwise disparate parts of the source data.

The project Wiki provides a deeper dive into these concepts.

Illustration

To illustrate some of these concepts, consider these samples:

---
hash:
  child_attr:
    key: 5280

This value, 5280, can be identified via YAML Path as any of:

1. hash.child_attr.key (dot-notation)
2. hash.child_attr[.=key] (search all child keys for one named, key, and yield its value)
3. /hash/child_attr/key (same as 1 but in forward-slash notation)
4. /hash/child_attr[.=key] (same as 2 but in forward-slash notation)

---
aliases:
  - &first_anchor Simple string value

With YAML Path, you can select this anchored value by any of these equivalent expressions:

1. aliases[0] (explicit array element number)
2. aliases.0 (implicit array element number in dot-notation)
3. aliases[&first_anchor] (search by Anchor name)
4. aliases[.^Simple] (search for any elements starting with "Simple")
5. aliases[.%string] (search for any elements containing "string")
6. aliases[.$value] (search for any elements ending with "value")
7. aliases[.=~/^(\b[Ss][a-z]+\s){2}[a-z]+$/] (search for any elements matching a complex Python Regular Expression, which happens to match the example)
8. /aliases[0] (same as 1 but in forward-slash notation)
9. /aliases/0 (same as 2 but in forward-slash notation)
10. /aliases[&first_anchor] (same as 3 but in forward-slash notation)

---
users:
  - name: User One
    password: ENC[PKCS7,MIIBiQY...Jk==]
    roles:
      - Writers
  - name: User Two
    password: ENC[PKCS7,MIIBiQY...vF==]
    roles:
      - Power Users
      - Editors

With an example like this, YAML Path enables:

• selection of single nodes: /users/0/roles/0 = Writers
• all children nodes of any given parent: /users/1/roles = ["Power Users", "Editors"]
• searching by a child attribute: /users[name="User One"]/password = Some decrypted value, provided you have the appropriate EYAML keys
• pass-through selections against arrays-of-hashes: /users/roles = ["Writers"]\n["Power Users", "Editors"] (each user's list of roles are a separate result)
• collection of disparate results: (/users/name) = ["User One", "User Two"] (all names appear in a single result instead of one per line)

For a deeper exploration of YAML Path's capabilities, please visit the project Wiki.

Supported YAML Path Segments

A YAML Path segment is the text between separators which identifies zero or more parent or leaf nodes within the data structure. For dot-notation, a path like hash.key identifies two segments: hash (a parent node) and key (a leaf node). The same path in forward-slash notation would be: /hash/key.

YAML Path understands these segment types:

• Top-level Hash key selection: key
• Explicit top-level array element selection: [#] where # is the zero-based element number; # can also be negative, causing the element to be selected from the end of the Array
• Implicit array element selection or numbered hash key selection: # where # is the 0-based element number or exact name of a hash key which is itself a number
• Top-level (Hash) Anchor lookups: &anchor_name (the & is required to indicate you are seeking an Anchor by name)
• Hash sub-keys: hash.child.key or /hash/child/key
• Demarcation for dotted Hash keys: hash.'dotted.child.key' or hash."dotted.child.key" (not necessary when using forward-slash notation, /hash/dotted.child.key)
• Named Array element selection: array[#], array.#, /array[#], or /array/# where array is the name of the Hash key containing Array data and # is the 0-based element number
• Anchor lookups in named Arrays: array[&anchor_name] where array is the name of the Hash key containing Array data and both of the [] pair and & are required to indicate you are seeking an Anchor by name within an Array
• Array slicing: array[start#:stop#] where start# is the first inclusive, zero-based element and stop# is the last exclusive element to select; either or both can be negative, causing the elements to be selected from the end of the Array; when start# and stop# are identical, it is the same as array[start#]
• Hash slicing: hash[min:max] where min and max are alphanumeric terms between which the Hash's keys are compared
• Escape symbol recognition: hash.dotted\.child\.key, /hash/whacked\/child\/key, and keys_with_\\slashes
• Hash attribute searches (which can return zero or more matches):
  • Exact match: hash[name=admin]
  • Starts With match: hash[name^adm]
  • Ends With match: hash[name$min]
  • Contains match: hash[name%dmi]
  • Less Than match: hash[access_level<500]
  • Greater Than match: hash[access_level>0]
  • Less Than or Equal match: hash[access_level<=100]
  • Greater Than or Equal match: hash[access_level>=0]
  • Python Regular Expression matches: hash[access_level=~/^\D+$/] (the / Regular Expression delimiter can be substituted for any character you need, except white-space; note that / does not interfere with forward-slash notation and it does not need to be escaped because the entire search expression is contained within a [] pair)
  • Invert any match with !, like: hash[name!=admin] or even hash[!name=admin] (the former syntax is used when YAML Paths are stringified but both forms are equivalent)
  • Demarcate and/or escape expression operands, like: hash[full\ name="Some User\'s Name"] (note that embedded, single ' and " must be escaped lest they be deemed unmatched demarcation pairings)
  • Multi-level matching: hash[name%admin].pass[encrypted!^ENC\[] or /hash[name%admin]/pass[encrypted!^ENC\[]
  • Descendent node searches: structure[has.descendant.with=something].has.another.field or /structure[/has/descendant/with=something]/has/another/field
• Array element searches with all of the search methods above via . (yields any matching elements): array[.>9000]
• Hash key-name searches with all of the search methods above via . (yields their values, not the keys themselves): hash[.^app_]
• Array-of-Hashes Pass-Through Selection: Omit a selector for the elements of an Array-of-Hashes and all matching Hash attributes at that level will be yielded (or searched when there is more to the path). For example, warriors[1].power_level or /warriors[1]/power_level will return the power_level attribute of only the second Hash in an Array-of-Hashes while warriors.power_level or /warriors/power_level will return the power_level attribute of every Hash in the same Array-of-Hashes. Of course these results can be filtered in multiple ways, like warriors[power_level>9000], /warriors[power_level>9000], warriors.power_level[.>9000], and /warriors/power_level[.>9000] all yield only the power_level from all warriors with power_levels over 9,000 within the same array of warrior hashes.
• Unordered Set value accessing and searching with all above search methods.
• Wildcard Searches: The * symbol can be used as shorthand for the [] search operator against text keys and values: /warriors/name/Go*; it also returns every immediate child, regardless its key or value.
• Deep Traversals: The ** symbol pair deeply traverses the document:
  • When it is the last or only segment of a YAML Path, it selects every leaf node from the remainder of the document's tree: /shows/**
  • When another segment follows, it matches every node within the remainder of the document's tree for which the following (and subsequent) segments match: /shows/**/name/Star*
• Search Keywords: Advanced search capabilities not otherwise possible using other YAML Path segments. Taking the form of [KEYWORD(PARAMETERS)], these keywords are deeply explored on the Wiki and include:
  • [distinct(NAME)]: Match exactly one of every value within collections, discarding duplicates; i.e.: [1, 2, 2, 3] has distinct values, [1, 2, 3]
  • [has_child(NAME)]: Match nodes having a named child key
  • [max([NAME])]: Match nodes having the maximum value
  • [min([NAME])]: Match nodes having the minimum value
  • [name()]: Match only the name of the present node, discarding all children
  • [parent([STEPS])], Step up 1-N levels in the document from the present node
  • [unique(NAME)]: Match only values which have no duplicates within collections; i.e.: [1, 2, 2, 3] has unique values, [1, 3]
• Collectors: Placing any portion of the YAML Path within parenthesis defines a virtual list collector, like (YAML Path); concatenation, exclusion, and intersection operators are supported -- +, -, and &, respectively -- along with nesting, like (...)-((...)+(...))&(...)
• Complex combinations: some::deep.hierarchy[with!=""].'any.valid'[.=~/(yaml|json)/][data%structure].or.complexity[4].2 or /some::deep/hierarchy[with!=""]/any*.*valid[.=~/(yaml|json)/][data%structure]/or/compl*xity[4]/2/**

This implementation of YAML Path encourages creativity. Use whichever notation and segment types that make the most sense to you in each application.

The project Wiki provides more illustrative details of YAML Path Segments.

Installing

Some OS distributions offer some versions of yamlpath -- and its dependencies -- via packages. While these versions of yamlpath are often outdated, they can be convenient to install using your OS' native package manager (apt, yum, npm, and such). Otherwise, Python's own package manager pip will always offer the latest version of yamlpath and -- even better -- can be isolated to ephemeral or longer-lasting virtual Python environments.

Requirements

This project requires Python 3. It is rigorously tested against Pythons 3.7 through 3.11 (support for Python 3.6 was dropped 10 FEB 2024). Most operating systems and distributions have access to Python 3 even if only Python 2 -- or no Python, at all -- came pre-installed. It is generally safe to have more than one version of Python on your system at the same time, especially when using virtual Python environments.

yamlpath depends on ruamel.yaml (derived from and greatly extending PyYAML) and python-dateutil. When using OS-native packages or pip, you do not need to pre-install these libraries yourself except under extraordinary circumstances like using very old versions of pip or its own dependency, setuptools.

Using pip

Like most others, this Python project is published to PyPI so that it can be easily installed via Python's pip command (or its version-specific pip3, pip3.7, and such depending on how your Python was installed).

Python's pip command is ever-changing. It is updated very frequently. This command further depends on other libraries to do its job, namely setuptools. It so happens that setuptools is also updated very frequently. Both of these are separate from Python itself, despite versions of them being pre-installed with Python. It is your responsibility to keep pip and setuptools up-to-date. When pip or setuptools become outdated, you will experience errors when trying to install newer Python packages like yamlpath unless you preinstall such packages' dependencies. In the case of yamlpath, this means you'd need to preinstall ruamel.yaml and python-dateutil if you cannot or choose not to upgrade pip and/or setuptools.

As long as your pip and setuptools are up-to-date, installing yamlpath is as simple as a single command (the "3.7" suffix to the pip command is optional, depending on how your Python 3 was installed):

pip3.7 install yamlpath

Very Old Versions of pip or its setuptools Dependency

Very old versions of Python 3 ship with seriously outdated versions of pip and its setuptools dependency. When using versions of pip older than 18.1 or setuptools older than version 46.4.0, you will not be able to install yamlpath with a single command. In this case, you have two options: either pre-install ruamel.yaml and python-dateutil before installing yamlpath or update pip and/or setuptools to at least the minimum required versions so pip can auto-determine and install dependencies. This issue is not unique to yamlpath.

Upgrading pip and setuptools is trivially simple as long as you have sufficient access rights to do so on your local machine. Depending on your situation, you may need to prefix these with sudo and/or you may need to substitute python3 and pip3 for python and pip, or even python3.7 and pip3.7 (or another specific version of Python 3), respectively. To reiterate that this project requires Python 3, these sample commands will be demonstrated using such prefixes:

python3.7 -m pip install --upgrade pip
pip3.7 install --upgrade setuptools

When you cannot or will not update pip or setuptools, just pre-install ruamel.yaml and python-dateutil before yamlpath. Each must be installed separately and in order, like this (you cannot combine these installations into a single command):

pip3.7 install ruamel.yaml python-dateutil
pip3.7 install yamlpath

The downside to choosing this manual installation path is that you may end up with an incompatible version of ruamel.yaml or python-dateutil. This will manifest either as an inability to install yamlpath at all, or only certain versions of yamlpath, or yamlpath may experience unexpected errors caused by the incompatible code. For the best experience, you are strongly encouraged to just keep pip and setuptools up-to-date, particularly as a routine part of installing any new Python packages.

Installing EYAML (Optional)

EYAML support is entirely optional. You do not need EYAML to use YAML Path. That YAML Path supports EYAML is a service to a substantial audience: Puppet users. At the time of this writing, EYAML (classified as a Hiera back-end/plug-in) is available only as a Ruby Gem. That said, it provides a command-line tool, eyaml, which can be employed by this otherwise Python project. To enjoy EYAML support, install compatible versions of ruby and rubygems, then execute:

gem install hiera-eyaml

If this puts the eyaml command on your system PATH, nothing more need be done apart from generating or obtaining your encryption keys. Otherwise, you can tell YAML Path library and tools where to find the eyaml command.

Based on ruamel.yaml

In order to support the best available YAML editing capability (so called, round-trip editing with support for comment preservation), this project is based on ruamel.yaml for Python 3. While ruamel.yaml is based on PyYAML -- Python's "standard" YAML library -- ruamel.yaml is objectively better than PyYAML, which lacks critical round-trip editing capabilities as well as up-to-date YAML/Compatible data parsing capabilities (at the time of this writing).

Should PyYAML ever merge with -- or at least, catch up with -- ruamel.yaml, this project can be (lightly) adapted to depend on it, instead. These conversations may offer some insight into when or whether this might happen:

• Is this time to pass the baton?
• Rebase off ruamel? - many new valuable features

The Files of This Project

This repository contains:

1. Generally-useful Python library files. These contain the reusable core of this project's YAML Path capabilities.
2. Some implementations of those libraries, exhibiting their capabilities and simple-to-use APIs as command-line tools.
3. Various support, documentation, and build files.

Command-Line Tools

This project provides some command-line tool implementations which utilize YAML Path. For some use-case examples of these tools, see below.

The supplied command-line tools include:

• eyaml-rotate-keys

usage: eyaml-rotate-keys [-h] [-V] [-d | -v | -q] [-b] [-x EYAML]
                         -i OLDPRIVATEKEY -c OLDPUBLICKEY
                         -r NEWPRIVATEKEY -u NEWPUBLICKEY
                         YAML_FILE [YAML_FILE ...]

Rotates the encryption keys used for all EYAML values within a set of YAML
files, decrypting with old keys and re-encrypting using replacement keys.

positional arguments:
  YAML_FILE             one or more YAML files containing EYAML values

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  -d, --debug           output debugging details
  -v, --verbose         increase output verbosity
  -q, --quiet           suppress all output except errors
  -b, --backup          save a backup of each modified YAML_FILE with an extra
                        .bak file-extension
  -x EYAML, --eyaml EYAML
                        the eyaml binary to use when it isn't on the PATH

EYAML_KEYS:
  All key arguments are required

  -r NEWPRIVATEKEY, --newprivatekey NEWPRIVATEKEY
                        the new EYAML private key
  -u NEWPUBLICKEY, --newpublickey NEWPUBLICKEY
                        the new EYAML public key
  -i OLDPRIVATEKEY, --oldprivatekey OLDPRIVATEKEY
                        the old EYAML private key
  -c OLDPUBLICKEY, --oldpublickey OLDPUBLICKEY
                        the old EYAML public key

Any YAML_FILEs lacking EYAML values will not be modified (or backed up, even
when -b/--backup is specified).

• yaml-diff

usage: yaml-diff [-h] [-V] [-a] [-s | -o]
                 [-t ['.', '/', 'auto', 'dot', 'fslash']] [-x EYAML]
                 [-r PRIVATEKEY] [-u PUBLICKEY] [-E] [-d | -v | -q]
                 YAML_FILE YAML_FILE

Calculate the functional difference between two YAML/JSON/Compatible
documents. Immaterial differences (which YAML/JSON parsers discard) are
ignored. EYAML can be employed to compare encrypted values.

positional arguments:
  YAML_FILE             exactly two YAML/JSON/compatible files to compare; use
                        - to read one document from STDIN

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  -a, --sync-arrays     Synchronize array elements before comparing them,
                        resulting only in ADD, DELETE, and SAME differences
                        (no CHANGEs because the positions of elements are
                        disregarded); Array-of-Hash elements must completely
                        and perfectly match or they will be deemed additions
                        or deletions
  -s, --same            Show all nodes which are the same in addition to
                        differences
  -o, --onlysame        Show only nodes which are the same, still reporting
                        that differences exist -- when they do -- with an
                        exit-state of 1
  -t ['.', '/', 'auto', 'dot', 'fslash'], --pathsep ['.', '/', 'auto', 'dot', 'fslash']
                        indicate which YAML Path separator to use when
                        rendering results; default=dot
  -d, --debug           output debugging details
  -v, --verbose         increase output verbosity
  -q, --quiet           suppress all output except system errors

EYAML options:
  Left unset, the EYAML keys will default to your system or user defaults.
  Both keys must be set either here or in your system or user EYAML
  configuration file when using EYAML.

  -x EYAML, --eyaml EYAML
                        the eyaml binary to use when it isn't on the PATH
  -r PRIVATEKEY, --privatekey PRIVATEKEY
                        EYAML private key
  -u PUBLICKEY, --publickey PUBLICKEY
                        EYAML public key
  -E, --ignore-eyaml-values
                        Do not use EYAML to compare encrypted data; rather,
                        treat ENC[...] values as regular strings

Only one YAML_FILE may be the - pseudo-file for reading from STDIN. For more
information about YAML Paths, please visit
https://github.com/wwkimball/yamlpath.

• yaml-get

usage: yaml-get [-h] [-V] -p YAML_PATH
                [-t ['.', '/', 'auto', 'dot', 'fslash']] [-S] [-x EYAML]
                [-r PRIVATEKEY] [-u PUBLICKEY] [-d | -v | -q]
                [YAML_FILE]

Retrieves one or more values from a YAML/JSON/Compatible file at a specified
YAML Path. Output is printed to STDOUT, one line per result. When a result is
a complex data-type (Array or Hash), a JSON dump is produced to represent it.
EYAML can be employed to decrypt the values.

positional arguments:
  YAML_FILE             the YAML file to query; omit or use - to read from
                        STDIN

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  -t ['.', '/', 'auto', 'dot', 'fslash'], --pathsep ['.', '/', 'auto', 'dot', 'fslash']
                        indicate which YAML Path separator to use when
                        rendering results; default=dot
  -S, --nostdin         Do not implicitly read from STDIN, even when YAML_FILE
                        is not set and the session is non-TTY
  -d, --debug           output debugging details
  -v, --verbose         increase output verbosity
  -q, --quiet           suppress all output except errors

required settings:
  -p YAML_PATH, --query YAML_PATH
                        YAML Path to query

EYAML options:
  Left unset, the EYAML keys will default to your system or user defaults.
  Both keys must be set either here or in your system or user EYAML
  configuration file when using EYAML.

  -x EYAML, --eyaml EYAML
                        the eyaml binary to use when it isn't on the PATH
  -r PRIVATEKEY, --privatekey PRIVATEKEY
                        EYAML private key
  -u PUBLICKEY, --publickey PUBLICKEY
                        EYAML public key

For more information about YAML Paths, please visit
https://github.com/wwkimball/yamlpath.

• yaml-merge

usage: yaml-merge [-h] [-V] [-c CONFIG] [-a {stop,left,right,rename}]
                  [-A {all,left,right,unique}] [-H {deep,left,right}]
                  [-O {all,deep,left,right,unique}] [-m YAML_PATH]
                  [-o OUTPUT | -w OVERWRITE] [-b] [-D {auto,json,yaml}] [-S]
                  [-d | -v | -q]
                  [YAML_FILE [YAML_FILE ...]]

Merges two or more YAML/JSON/Compatible files together.

positional arguments:
  YAML_FILE             one or more YAML files to merge, order-significant;
                        omit or use - to read from STDIN

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  -c CONFIG, --config CONFIG
                        INI syle configuration file for YAML Path specified
                        merge control options
  -a {stop,left,right,rename}, --anchors {stop,left,right,rename}
                        means by which Anchor name conflicts are resolved
                        (overrides [defaults]anchors set via --config|-c and
                        cannot be overridden by [rules] because Anchors apply
                        to the whole file); default=stop
  -A {all,left,right,unique}, --arrays {all,left,right,unique}
                        default means by which Arrays are merged together
                        (overrides [defaults]arrays but is overridden on a
                        YAML Path basis via --config|-c); default=all
  -H {deep,left,right}, --hashes {deep,left,right}
                        default means by which Hashes are merged together
                        (overrides [defaults]hashes but is overridden on a
                        YAML Path basis in [rules] set via --config|-c);
                        default=deep
  -O {all,deep,left,right,unique}, --aoh {all,deep,left,right,unique}
                        default means by which Arrays-of-Hashes are merged
                        together (overrides [defaults]aoh but is overridden on
                        a YAML Path basis in [rules] set via --config|-c);
                        default=all
  -m YAML_PATH, --mergeat YAML_PATH
                        YAML Path indicating where in left YAML_FILE the right
                        YAML_FILE content is to be merged; default=/
  -o OUTPUT, --output OUTPUT
                        Write the merged result to the indicated nonexistent
                        file
  -w OVERWRITE, --overwrite OVERWRITE
                        Write the merged result to the indicated file; will
                        replace the file when it already exists
  -b, --backup          save a backup OVERWRITE file with an extra .bak
                        file-extension; applies only to OVERWRITE
  -D {auto,json,yaml}, --document-format {auto,json,yaml}
                        Force the merged result to be presented in one of the
                        supported formats or let it automatically match the
                        known file-name extension of OUTPUT|OVERWRITE (when
                        provided), or match the type of the first document;
                        default=auto
  -S, --nostdin         Do not implicitly read from STDIN, even when there are
                        no - pseudo-files in YAML_FILEs with a non-TTY session
  -d, --debug           output debugging details
  -v, --verbose         increase output verbosity
  -q, --quiet           suppress all output except errors (implied when
                        -o|--output is not set)

            The CONFIG file is an INI file with up to three sections:
            [defaults] Sets equivalents of -a|--anchors, -A|--arrays,
                       -H|--hashes, and -O|--aoh.
            [rules]    Each entry is a YAML Path assigning -A|--arrays,
                       -H|--hashes, or -O|--aoh for precise nodes.
            [keys]     Wherever -O|--aoh=DEEP, each entry is treated as a
                       record with an identity key.  In order to match RHS
                       records to LHS records, a key must be known and is
                       identified on a YAML Path basis via this section.
                       Where not specified, the first attribute of the first
                       record in the Array-of-Hashes is presumed the identity
                       key for all records in the set.

            The left-to-right order of YAML_FILEs is significant.  Except
            when this behavior is deliberately altered by your options, data
            from files on the right overrides data in files to their left.
            Only one input file may be the - pseudo-file (read from STDIN).
            When no YAML_FILEs are provided, - will be inferred as long as you
            are running this program without a TTY (unless you set
            --nostdin|-S).  Any file, including input from STDIN, may be a
            multi-document YAML or JSON file.

            For more information about YAML Paths, please visit
            https://github.com/wwkimball/yamlpath.

• yaml-paths

usage: yaml-paths [-h] [-V] -s EXPRESSION [-c EXPRESSION] [-m] [-L] [-F] [-X]
                  [-P] [-n] [-t ['.', '/', 'auto', 'dot', 'fslash']]
                  [-i | -k | -K] [-a] [-A | -Y | -y | -l] [-e] [-x EYAML]
                  [-r PRIVATEKEY] [-u PUBLICKEY] [-S] [-d | -v | -q]
                  [YAML_FILE [YAML_FILE ...]]

Returns zero or more YAML Paths indicating where in given YAML/JSON/Compatible
data one or more search expressions match. Values, keys, and/or anchors can be
searched. EYAML can be employed to search encrypted values.

positional arguments:
  YAML_FILE             one or more YAML files to search; omit or use - to
                        read from STDIN

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  -c EXPRESSION, --except EXPRESSION
                        except results matching this search expression; can be
                        set more than once
  -m, --expand          expand matching parent nodes to list all permissible
                        child leaf nodes (see "reference handling options" for
                        restrictions)
  -t ['.', '/', 'auto', 'dot', 'fslash'], --pathsep ['.', '/', 'auto', 'dot', 'fslash']
                        indicate which YAML Path separator to use when
                        rendering results; default=dot
  -a, --refnames        also search the names of &anchor and *alias references
  -S, --nostdin         Do not implicitly read from STDIN, even when there are
                        no - pseudo-files in YAML_FILEs with a non-TTY session
  -d, --debug           output debugging details
  -v, --verbose         increase output verbosity
  -q, --quiet           suppress all non-result output except errors

required settings:
  -s EXPRESSION, --search EXPRESSION
                        the search expression; can be set more than once

result printing options:
  -L, --values          print the values or elements along with each YAML Path
                        (complex results are emitted as JSON; use --expand to
                        emit only simple values)
  -F, --nofile          omit source file path and name decorators from the
                        output (applies only when searching multiple files)
  -X, --noexpression    omit search expression decorators from the output
  -P, --noyamlpath      omit YAML Paths from the output (useful with --values
                        or to indicate whether a file has any matches without
                        printing them all, perhaps especially with
                        --noexpression)
  -n, --noescape        omit escape characters from special characters in
                        printed YAML Paths; this is unsafe for feeding the
                        resulting YAML Paths into other YAML Path commands
                        because the symbols that would be escaped have special
                        meaning to YAML Path processors

key name searching options:
  -i, --ignorekeynames  (default) do not search key names
  -k, --keynames        search key names in addition to values and array
                        elements
  -K, --onlykeynames    only search key names (ignore all values and array
                        elements)

reference handling options:
  Indicate how to treat anchor and alias references. An anchor is an
  original, reusable key or value. All aliases become replaced by the
  anchors they reference when YAML data is read. These options specify how
  to handle this duplication of keys and values. Note that the default
  behavior includes all aliased keys but not aliased values.

  -A, --anchorsonly     include only original matching key and value anchors
                        in results, discarding all aliased keys and values
                        (including child nodes)
  -Y, --allowkeyaliases
                        (default) include matching key aliases, permitting
                        search traversal into their child nodes
  -y, --allowvaluealiases
                        include matching value aliases (does not permit search
                        traversal into aliased keys)
  -l, --allowaliases    include all matching key and value aliases

EYAML options:
  Left unset, the EYAML keys will default to your system or user defaults.
  Both keys must be set either here or in your system or user EYAML
  configuration file when using EYAML.

  -e, --decrypt         decrypt EYAML values in order to search them
                        (otherwise, search the encrypted blob)
  -x EYAML, --eyaml EYAML
                        the eyaml binary to use when it isn't on the PATH
  -r PRIVATEKEY, --privatekey PRIVATEKEY
                        EYAML private key
  -u PUBLICKEY, --publickey PUBLICKEY
                        EYAML public key

A search or exception EXPRESSION takes the form of a YAML Path search operator
-- %, $, =, ^, >, <, >=, <=, =~, or ! -- followed by the search term, omitting
the left-hand operand. For more information about YAML Paths, please visit
https://github.com/wwkimball/yamlpath/wiki. To report issues with this tool or
to request enhancements, please visit
https://github.com/wwkimball/yamlpath/issues.

• yaml-set

usage: yaml-set [-h] [-V] -g YAML_PATH
                [-a VALUE | -A ANCHOR | -f FILE | -i | -R LENGTH | -N | -D]
                [-F {bare,boolean,default,dquote,float,folded,int,literal,squote}]
                [-c CHECK] [-s YAML_PATH] [-m] [-b]
                [-t ['.', '/', 'auto', 'dot', 'fslash']] [-M CHARS] [-H ANCHOR]
                [-T TAG] [-e] [-x EYAML] [-r PRIVATEKEY] [-u PUBLICKEY] [-S]
                [-d | -v | -q]
                [YAML_FILE]

Changes one or more Scalar values in a YAML/JSON/Compatible document at a
specified YAML Path. Matched values can be checked before they are replaced to
mitigate accidental change. When matching singular results, the value can be
archived to another key before it is replaced. Further, EYAML can be employed to
encrypt the new values and/or decrypt an old value before checking it.

positional arguments:
  YAML_FILE             the YAML file to update; omit or use - to read from
                        STDIN

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  -F {bare,boolean,default,dquote,float,folded,int,literal,squote}, --format {bare,boolean,default,dquote,float,folded,int,literal,squote}
                        override automatic formatting of the new value
  -c CHECK, --check CHECK
                        check the value before replacing it
  -s YAML_PATH, --saveto YAML_PATH
                        save the old value to YAML_PATH before replacing it;
                        implies --mustexist
  -m, --mustexist       require that the --change YAML_PATH already exist in
                        YAML_FILE
  -b, --backup          save a backup YAML_FILE with an extra .bak file-
                        extension
  -t ['.', '/', 'auto', 'dot', 'fslash'], --pathsep ['.', '/', 'auto', 'dot', 'fslash']
                        indicate which YAML Path separator to use when rendering
                        results; default=dot
  -M CHARS, --random-from CHARS
                        characters from which to build a value for --random;
                        default=all upper- and lower-case letters and all digits
  -H ANCHOR, --anchor ANCHOR
                        when --aliasof|-A points to a value which is not already
                        Anchored, a new Anchor with this name is created;
                        renames an existing Anchor if already set
  -T TAG, --tag TAG     assign a custom YAML (data-type) tag to the changed
                        nodes; can be used without other input options to assign
                        or change a tag
  -S, --nostdin         Do not implicitly read from STDIN, even when there is no
                        YAML_FILE with a non-TTY session
  -d, --debug           output debugging details
  -v, --verbose         increase output verbosity
  -q, --quiet           suppress all output except errors

required settings:
  -g YAML_PATH, --change YAML_PATH
                        YAML Path where the target value is found

input options:
  -a VALUE, --value VALUE
                        set the new value from the command-line instead of STDIN
  -A ANCHOR, --aliasof ANCHOR
                        set the value as a YAML Alias of an existing Anchor, by
                        name (merely copies the target value for non-YAML files)
  -f FILE, --file FILE  read the new value from file (discarding any trailing
                        new-lines)
  -i, --stdin           accept the new value from STDIN (best for sensitive
                        data)
  -R LENGTH, --random LENGTH
                        randomly generate a replacement value of a set length
  -N, --null            sets the value to null
  -D, --delete          delete rather than change target node(s); implies
                        --mustexist|-m

EYAML options:
  Left unset, the EYAML keys will default to your system or user defaults. You
  do not need to supply a private key unless you enable --check and the old
  value is encrypted.

  -e, --eyamlcrypt      encrypt the new value using EYAML
  -x EYAML, --eyaml EYAML
                        the eyaml binary to use when it isn't on the PATH
  -r PRIVATEKEY, --privatekey PRIVATEKEY
                        EYAML private key
  -u PUBLICKEY, --publickey PUBLICKEY
                        EYAML public key

When no changes are made, no backup is created, even when -b/--backup is
specified. For more information about YAML Paths, please visit
https://github.com/wwkimball/yamlpath/wiki. To report issues with this tool or
to request enhancements, please visit
https://github.com/wwkimball/yamlpath/issues.

• yaml-validate

usage: yaml-validate [-h] [-V] [-S] [-d | -v | -q] [YAML_FILE [YAML_FILE ...]]

Validate YAML, JSON, and compatible files.

positional arguments:
  YAML_FILE      one or more single- or multi-document YAML/JSON/compatible
                 files to validate; omit or use - to read from STDIN

optional arguments:
  -h, --help     show this help message and exit
  -V, --version  show program's version number and exit
  -S, --nostdin  Do not implicitly read from STDIN, even when there are no -
                 pseudo-files in YAML_FILEs with a non-TTY session
  -d, --debug    output debugging details
  -v, --verbose  increase output verbosity (show valid documents)
  -q, --quiet    suppress all output except system errors

Except when suppressing all report output with --quiet|-q, validation issues
are printed to STDOUT (not STDERR). Further, the exit-state will report 0 when
there are no issues, 1 when there is an issue with the supplied command-line
arguments, or 2 when validation has failed for any document.

Libraries

While there are several supporting library files like enumerations, types, and exceptions, the most interesting library files include:

• yamlpath.py -- The core YAML Path parser logic.
• processor.py -- Processes YAMLPath instances to read or write data to YAML/Compatible sources.
• eyamlprocessor.py -- Extends the Processor class to support EYAML data encryption and decryption.
• merger.py -- The core document merging logic.

Basic Usage

The files of this project can be used either as command-line tools or as libraries to supplement your own work.

Basic Usage: Command-Line Tools

The command-line tools are self-documented and their documentation is captured above for easy reference. Simply pass --help to them in order to obtain the same detailed documentation.

Please review the comprehensive test_commands_*.py unit tests to explore samples of YAML files and the many ways these tools help get and set their data.

The following are some simple examples of their typical use-cases.

Rotate Your EYAML Keys

If the eyaml command is already on your PATH (if not, be sure to also supply the optional --eyaml or -x argument):

eyaml-rotate-keys \
  --oldprivatekey=~/old-keys/private_key.pkcs7.pem \
  --oldpublickey=~/old-keys/public_key.pkcs7.pem \
  --newprivatekey=~/new-keys/private_key.pkcs7.pem \
  --newpublickey=~/new-keys/public_key.pkcs7.pem \
  my_1st_yaml_file.yaml my_2nd_yaml_file.eyaml ... my_Nth_yaml_file.yaml

You could combine this with find and xargs if your E/YAML file are dispersed through a directory hierarchy, as with Hiera data.

Get the Differences Between Two Documents

For routine use:

yaml-diff yaml_file1.yaml yaml_file2.yaml

Output is very similar to that of standard GNU diff against text files, except it is generated against the data within the input files. This excludes evaluating purely structural and immaterial differences between them like value demarcation, white-space, and comments. When you need to evaluate the two files as if they were just text files, use GNU diff or any of its clones.

To see all identical entries along with differences:

yaml-diff --same yaml_file1.yaml yaml_file2.yaml

To see only entries which are identical between the documents:

yaml-diff --onlysame yaml_file1.yaml yaml_file2.yaml

Advanced: Arrays can be evaluated such that they are synchronized before evaluation. Rather than compare elements by identical index in both documents -- reporting differences between them as changes and any additional elements as additions or deletions -- they can instead be compared by matching up all identical elements and then reporting only those values which are unique to either document (and optionally identical matches).

yaml-diff --sync-arrays yaml_file1.yaml yaml_file2.yaml

Get a YAML/JSON/Compatible Value

At its simplest:

yaml-get \
  --query=see.documentation.above.for.many.samples \
  my_yaml_file.yaml

Search For YAML Paths

Simplest use:

yaml-paths \
  --search=%word \
  /some/directory/*.yaml

Search for multiple expressions and exclude unwanted results:

yaml-paths \
  --search=^another \
  --search=$word \
  --except=%bad \
  /some/directory/*.yaml

Return all leaf nodes under matching parents (most useful when matching against Hash keys and you only want the original leaf nodes beneath them):

yaml-paths \
  --expand \
  --keynames \
  --search==parent_node \
  /some/directory/*.yaml

Change a YAML/JSON/Compatible Value

For a no-frills change to a YAML file with deeply nested Hash structures:

yaml-set \
  --change=see.documentation.above.for.many.samples \
  --value="New Value" \
  my_yaml_file.yaml

To rotate a password, preserving the old password perhaps so your automation can apply the new password to your application(s):

yaml-set \
  --mustexist \
  --change=the.new.password \
  --saveto=the.old.password \
  --value="New Password" \
  my_yaml_file.yaml

For the extremely cautious, you could check the old password before rotating it and save a backup of the original file:

yaml-set \
  --mustexist \
  --change=the.new.password \
  --saveto=the.old.password \
  --check="Old Password" \
  --value="New Password" \
  --backup \
  my_yaml_file.yaml

You can also add EYAML encryption (assuming the eyaml command is on your PATH; if not, you can pass --eyaml to specify its location). In this example, I add the optional --format=folded so that the long EYAML value is broken up into a multi-line value rather than one very long string. This is the preferred format for human legibility as well as EYAML consumers like Puppet. Note that --format has several other settings and applies only to new values.

yaml-set \
  --change=the.new.password \
  --mustexist \
  --saveto=the.old.password \
  --check="Old Password" \
  --value="New Password" \
  --eyamlcrypt \
  --format=folded \
  --backup \
  my_yaml_file.yaml

You can even tell EYAML which keys to use, if not your default system or user keys:

yaml-set \
  --change=the.new.password \
  --mustexist \
  --saveto=the.old.password \
  --check="Old Password" \
  --value="New Password" \
  --eyamlcrypt \
  --format=folded \
  --privatekey=/secret/keys/private_key.pkcs7.pem \
  --publickey=/secret/keys/public_key.pkcs7.pem \
  --backup \
  my_yaml_file.yaml

Note that for even greater security scenarios, you can keep the new value off of your command-line, process list, and command history by swapping out --value for one of --stdin, --file, or even --random LENGTH (use Python's strongest random value generator if you don't need to specify the replacement value in advance).

Merge YAML/JSON/Compatible Files

At its simplest, the yaml-merge command accepts two or more input files and merges them together from left-to-right, writing the result to STDOUT:

yaml-merge leftmost.yaml middle.yaml right.json

If you'd rather write the results to a new output file (which must not already exist):

yaml-merge \
  --output=newfile.yaml \
  leftmost.yaml \
  middle.yaml \
  right.json

Should you wish to merge the content of the files into a specific location (or even multiple locations) within the leftmost document, specify a YAML Path via the --mergeat or -m argument:

yaml-merge \
  --mergeat=/anywhere/within/the/document \
  leftmost.yaml \
  middle.yaml \
  right.json

To write arbitrary data from STDIN into a document, use the - pseudo-file:

echo "{arbitrary: [document, structure]}" | yaml-merge target.yaml -

Combine --mergeat or -m with the STDIN pseudo-file to control where the data is to be written:

echo "{arbitrary: [document, structure]}" | \
  yaml-merge \
    --mergeat=/anywhere/within/the/document \
    target.yaml -

There are many options for precisely controlling how the merge is performed, including the ability to specify complex rules on a YAML Path basis via a configuration file. Review the command's --help or the related Wiki for more detail.

Validate YAML/JSON/Compatible Documents

Validating the structure of YAML, JSON, and compatible files is as simple as running:

yaml-validate /path/to/any/files.yaml /path/to/more/files.json

In this default configuration, the command will output no report when all input documents are valid. It will also report an exit-state of zero (0). Should there be any validation errors, each will be printed to the screen and the exit-state will be 2. An exit-state of 1 means your command-line arguments were incorrect and an appropritae user error message will be displayed.

When there are validation issues, the offending file-name(s) and sub-document index(es) (zero-based) will be displayed along with a detailed validation error message.

Basic Usage: Libraries

As for the libraries, they are also heavily documented and the example implementations may perhaps serve as good copy-paste fodder (provided you give credit to the source). That said, here's a general flow/synopsis.

Initialize ruamel.yaml and These Helpers

Your preferences may differ, but I use this setup for round-trip YAML parsing and editing with ruamel.yaml. When you need to process EYAML encrypted data, replace yamlpath.Processor with yamlpath.eyaml.EYAMLProcessor and add error handling for yamlpath.eyaml.EYAMLCommandException.

Note also that these examples use ConsolePrinter to handle STDOUT and STDERR messaging. You don't have to. However, some kind of logger must be passed to these libraries so they can write messages somewhere. Your custom message handler or logger must provide the same API as ConsolePrinter; review the header documentation in consoleprinter.py for details. Generally speaking, it would be trivial to write your own custom wrapper for Python's standard logging facilities if you require targets other than STDOUT and STDERR.

from types import SimpleNamespace

from yamlpath.common import Parsers
from yamlpath.wrappers import ConsolePrinter
from yamlpath import Processor


# The various classes of this library must be able to write messages somewhere
# when things go bad.  This project provides a CLI-centric logging class named
# ConsolePrinter.  Even when not writing a CLI tool, you must still configure
# and pass ConsolePrinter or a class of your own with the same public API.  For
# just muting logging output -- except for unrecoverable errors -- you can use
# this simple configuration object:
logging_args = SimpleNamespace(quiet=True, verbose=False, debug=False)
log = ConsolePrinter(logging_args)

# Prep the YAML parser and round-trip editor (tweak to your needs).  You do not
# have to use Parsers.get_yaml_editor() but you must create a properly-
# configured instance of ruamel.yaml.YAML.
yaml = Parsers.get_yaml_editor()

# At this point, you'd load or parse your YAML file, stream, or string.  This
# example demonstrates loading YAML data from an external file.  You could also
# use the same function to load data from STDIN or even a String variable.  See
# the Parser class for more detail.
yaml_file = "your-file.yaml"
(yaml_data, doc_loaded) = Parsers.get_yaml_data(yaml, log, yaml_file)
if not doc_loaded:
    # There was an issue loading the file; an error message has already been
    # printed via ConsolePrinter.
    exit(1)

# Pass the logging facility and parsed YAML data to the YAMLPath Processor
processor = Processor(log, yaml_data)

# At this point, the Processor is ready to handle YAML Paths

Searching for YAML Nodes

These libraries use Generators to get nodes from parsed YAML data. Identify which node(s) to get via YAML Path strings. You should also catch yamlpath.exceptions.YAMLPathExceptions unless you prefer Python's native stack traces. When using EYAML, you should also catch yamlpath.eyaml.exceptions.EYAMLCommandExceptions for the same reason. Whether you are working with a single result or many, you should consume the Generator output with a pattern similar to:

from yamlpath import YAMLPath
from yamlpath.exceptions import YAMLPathException

yaml_path = YAMLPath("see.documentation.above.for.many.samples")
try:
    for node_coordinate in processor.get_nodes(yaml_path, mustexist=True):
        log.debug("Got {} from '{}'.".format(node_coordinate, yaml_path))
        # Do something with each node_coordinate.node (the actual data)
except YAMLPathException as ex:
    # If merely retrieving data, this exception may be deemed non-critical
    # unless your later code absolutely depends upon a result.
    log.error(ex)

Changing Values

At its simplest, you only need to supply the the YAML Path to one or more nodes to update, and the value to apply to them. Catching yamlpath.exceptions.YAMLPathException is optional but usually preferred over allowing Python to dump the call stack in front of your users. When using EYAML, the same applies to yamlpath.eyaml.exceptions.EYAMLCommandException.

from yamlpath.exceptions import YAMLPathException

try:
    processor.set_value(yaml_path, new_value)
except YAMLPathException as ex:
    log.critical(ex, 119)
except EYAMLCommandException as ex:
    log.critical(ex, 120)

Merging Documents

A document merge naturally requires at least two documents. At the code-level, this means two populated DOM objects (populated instances of yaml_data from above). You do not need to use a Processor for merging. In the least amount of code, a merge looks like:

from yamlpath.exceptions import YAMLPathException
from yamlpath.merger.exceptions import MergeException
from yamlpath.merger import Merger, MergerConfig

# Obtain or build the lhs_data and rhs_data objects using get_yaml_data or
# equivalent.

# You'll still need to supply a logger and some arguments used by the merge
# engine.  For purely default behavior, you could create args as a bare
# SimpleNamespace.  Initialize the new Merger instance with the LHS document.
merger = Merger(log, lhs_data, MergerConfig(log, args))

# Merge RHS into LHS
try:
    merger.merge_with(rhs_data)
except MergeException as mex:
    log.critical(mex, 129)
except YAMLPathException as yex:
    log.critical(yex, 130)

# At this point, merger.data is the merged result; do what you will with it,
# including merging more data into it.  When you are ready to dump (write)
# out the merged data, you must prepare the document and your
# ruamel.yaml.YAML instance -- usually obtained from func.get_yaml_editor()
# -- like this:
merger.prepare_for_dump(my_yaml_editor)