Functional Dependency Injection In Python (Inspired by the Reader Monad)

functional_dependency_injection.py

class Reader(object):
    pass

def to_camel_case(snake_str):
    parts = snake_str.split('_')
    return parts[0] + ''.join([s.capitalize() for s in parts[1:]])

def strip_leading_underscores(string):
    if string.startswith('_'):
        string = string[1:]
        string = string[1:] if string.startswith('_') else string
    return string

def inject_dependency_kwarg(dependency_name, dependency_value, *args):
    new_reader_name = \
        Reader.__name__ + to_camel_case(dependency_name).capitalize()
    new_reader = type(new_reader_name, (Reader,), {})()
    new_reader.__setattr__('__name__', new_reader_name)
    for func in args:
        func_name = strip_leading_underscores(func.__name__)
        partial_func = partial(func, **{dependency_name: dependency_value})
        partial_func.__setattr__('__name__', func_name)
        new_reader.__setattr__(func_name, partial_func)
    return new_reader

def inject_dependency_first_arg(dependency_name, dependency_value, *args):
    new_reader_name = \
        Reader.__name__ + to_camel_case(dependency_name).capitalize()
    new_reader = type(new_reader_name, (Reader,), {})()
    new_reader.__setattr__('__name__', new_reader_name)
    for func in args:
        func_name = strip_leading_underscores(func.__name__)
        partial_func = partial(func, dependency_value)
        partial_func.__setattr__('__name__', func_name)
        new_reader.__setattr__(func_name, partial_func)
    return new_reader

def import_public_attributes(obj, parent_frame_locals):
    """
    Imports the public attributes of the provided object so that they
    can be used without referencing the object from the parent frame (the caller).

    :param obj: The object whose public attributes to import
    :param parant_frame_locals: The dictionary returned from locals() in the
                                function call.

    Example:
        In [118]: def add(*args, logger=None):
             ...:     logger.info('adding %s' % str(args))
             ...:     return reduce(lambda acc, x: acc + x, args)
             ...:

        In [119]: logger_reader = inject_dependency_kwarg('logger', logger, add)

        In [120]: logger_reader.add(1,2,3)
        2018/12/18 14:25:42 adding (1, 2, 3)
        Out[120]: 6

        In [121]: logger_reader.add.__name__
        Out[121]: 'add'

        In [122]: import_public_attributes(logger_reader, locals())

        In [123]: add
        Out[123]: functools.partial(<function add at 0x127a47840>, logger=<logging.Logger object at 0x1279fc160>)

        In [125]: add(1,2,3)
        2018/12/18 16:58:39 adding (1, 2, 3)
        Out[125]: 6

        In [126]: one_reader = inject_dependency_first_arg('one', 1, logger_reader.add)

        In [128]: one_reader.add(2,3)
        2018/12/18 17:00:38 adding (1, 2, 3)
        Out[128]: 6

        In [129]: import_public_attributes(one_reader, locals())

        In [130]: add(2,3)
        2018/12/18 17:00:59 adding (1, 2, 3)
        Out[130]: 6
    """
    public_attrs = [attr for attr in dir(obj) if not attr.startswith('_')]
    for attr in public_attrs:
        parent_frame_locals[attr] = obj.__getattribute__(attr)

In [58]: def print_things():
    ...:     call_frame = sys._getframe(1)
    ...:     print(call_frame.f_locals)
    ...:     print(dir(call_frame))
    ...:

In [60]: def add(x, y, *args, z=None, **kwargs):
    ...:     print_things()
    ...:     from functools import reduce
    ...:     return x + y + (z if z else 0) + reduce(lambda b, acc: b + acc, list(args).extend(kwargs.values()) or [0])
    ...:
    ...:

In [63]: add(1,2,3,4,5,z=6,w=10)
{'kwargs': {'w': 10}, 'x': 1, 'z': 6, 'args': (3, 4, 5), 'y': 2}
['__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'clear', 'f_back', 'f_builtins', 'f_code', 'f_globals', 'f_lasti', 'f_lineno', 'f_locals', 'f_trace']

TODO: make it so that you don't have to pass in locals(), but rather, the function extracts the locals() out of the caller-frame itself. May or may not be possible...