format_string_interpolation.py

def format(st, *args, **kwds):
    """ Format with string interpolation
    String interpolation for python version < 3.6

    See also
    - https://www.python.org/dev/peps/pep-0498/
    - http://stackoverflow.com/questions/6618795/get-locals-from-calling-namespace-in-python
    """
    >>> a = 1
    >>> b = 2
    >>> format('{a} + {a} = {b}')
    '1 + 1 = 2'
    >>> format('{a} + {a} != {b}', b=3)
    '1 + 1 != 3'
    >>> format('{a} + {0} = {b}', 2, b=3)
    '1 + 2 = 3'

    # TODO access to external variables
    # >>> def nested1():
    # ...     a = 2
    # ...     def nested2():
    # ...         return format('{a} = {a} = {b}')
    # ...     return nested2()
    # >>> nested1()
    # '2 = 2 = 2'
    """
    import inspect
    frame = inspect.currentframe()
    try:
        d = {}
        d.update(frame.f_back.f_globals)
        d.update(frame.f_back.f_locals)
        d.update(kwds)
        return st.format(*args, **d)
    finally:
        del frame