POSIX Parameter Expansion

This is an experiment to create a Python library to enable POSIX parameter expansion from a string.

Obvious Test Cases

    >>> from parameter_expansion import expand
    >>> foo = 'abc/123-def.ghi'
    >>> # Bland Expansion
    >>> expand('abc $foo abc')
    'abc abc/123-def.ghi abc'
    >>> expand('abc${foo}abc')
    'abcabc/123-def.ghiabc'
    >>>
    >>> # Default Value Expansion
    >>> expand('-${foo:-bar}-')
    '-abc/123-def.ghi-'
    >>> expand('-${bar:-bar}-')
    '-bar-'

Default Value Expansion

    >>> foo = 'abc/123-def.ghi'
    >>> expand('abc $foo abc')
    'abc abc/123-def.ghi abc'
    >>> expand('abc${foo}abc')
    'abcabc/123-def.ghiabc'