Some extra python data containers (extra collections).

This project extends python`s core library collections module.

Getting started.

Installation.

We have no pypi account yet and we have no private pypi repository. So, you should install this package as usual with pip package manager in virtualenv or just globally from source:

pip install git+https://bitbucket.org/bfg-soft/collections_extension.git

If you want to install specific version or branch, you should execute:

pip install git+https://bitbucket.org/bfg-soft/collections_extension.git@v0.1.0

Content.

Native-like containers.

As we know, it is not recommended to inherit your own types from python`s core types like dict or tuple. This package provides some native-like types, such as:

• Tuple - tuple-like container for user types (immutable),
• List - list-like container for user types (mutable),
• Dict - dict-like container for user types (mutable),
• Map - MappingProxyType-like (dict without mutability) container for user types (immutable),
• Set - set-like container for user types (mutable)

Exception map container.

Container implements map of exception classes with inheritance check during searching key in map. For example, we have ExceptionMap:

from collections_extension import ExceptionMap

m = ExceptionMap({ValueError: 'somevalue'})

Imagine, that we catch UnicodeError somewere in program and we want to process it. Our processing is based on defined ExceptionMap m and we want to know what value we should send futher to the program runtime.

from collections_extension import ExceptionMap

m = ExceptionMap({ValueError: 'somevalue'})

...


def somefn():
 try:
  ...

 except UnicodeError:
  value = m[UnicodeError]

 except TypeError:
  value = m.get(TypeError)
  if value is None:
   raise

 else:
  value = None

 return value

ExceptionMap will search the hierarchy of key exception until it comes to Exception class. Only after that, map will raise KeyError exception.

Our map doesn`t contain UnicodeError key, but it contains ValueError. We know, that UnicodeError inherits ValueError exception class, so value during handling UnicodeError will be assigned to somevalue string.

During handling of TypeError exception we use method get of ExceptionMap. It doesn`t raise any exception, like method of type dict and returns default value (second argument, that should be passing to the method) or None.

Becides that, ExceptionMap allow to defined default_value during it`s initialization like:

from collections_extension import ExceptionMap

m = ExceptionMap({ValueError: 'somevalue'}, default_value='not none')

It overrides default value None, that will be returned when key does not exist and not default value has been passed.

Sqlalchemy declarative model map container.

Container implements map of sqlalchemy declarative meta classes as values and their tablenames as keys.

For example, you have module your_package.data.model with sqlalchemy declarative models.

You can make map of declarative models withthis code:

from collections_extension import SqlalchemyModelMap

MODEL_MAP = SqlalchemyModelMap.from_module_name('your_package.data.model')

After that, you can find all declarative model classes in this map (if your structured module correctly) by their tablename. For example MODEL_MAP['my_table'] will get you declarative model for my_table table.

Sqlalchemy declarative model schema map container.

Container implements map of marshmallow schema instances as values and tablenames of declarative model classes as keys.

Each marshmallow schema creates with special library marshmallow-sqlalchemy, which inspects declarative model classes and makes schema class as a result.

Typical usage:

from collections_extension import SqlalchemyModelMap, SqlalchemyModelSchemaMap

MODEL_MAP = SqlalchemyModelMap.from_module_name('your_package.data.model')
MODEL_SCHEMA_MAP = SqlalchemyModelSchemaMap.from_sqlalchemy_model_map(MODEL_MAP)

License.

This project is licensed under the MIT License - see the LICENSE.txt file for details.