Function formatting in Python - see usage

funcfmt.py

# This is more of an idea than a actual module - although you can use it as such.
# A few things you could do:
# - split the fmt_spec into comma-separated arguments which can be passed into the function
# - make a format method part of the class itself instead of splatting the object into format

class FormatFuncs(dict):
    def register(self, func):
        self[func.__name__] = type(func.__name__, (), {
            "__format__": lambda self, fmt_spec: func(fmt_spec)
        })()
        return func


# usage
if __name__ == "__main__":
    import random

    my_fmt_tools = FormatFuncs()

    @my_fmt_tools.register
    def rand(fmt_spec):
        return random.choice(fmt_spec.split("|"))

    @my_fmt_tools.register
    def upper(string):
        return string.upper()

    print("{upper:{desc}}: '{rand:hello|world}'".format(
        desc="chooses a random word from the phrase 'hello world'",
        **my_fmt_tools
    ))