Since my retirement a few years ago my habit of trying out sometimes useless or convoluted ideas has gone up a few notches.

Latest discovery is that `inspect.signature()` passes parameter annotations straight through. With a bit of function decorator hackery, you can get positional/keyword instrumented transformers.

@magic_params
def some_func(always_str:str):
   print(f"always_str is {type(always_str)} with a value of {repr(always_str)}")

>>some_func(123)
always_str is  with a value of "'123'"

another example

def reversed_str(raw):
    if not isinstance(raw, str):
        raw = str(raw)

    return raw[::-1]

@magic_decorator
def goofy_func(bizarro:reversed_str):
    return bizarro

assert goofy_func("Hello World") == "dlroW olleH"

A working proof of concept

In one of my pet projects, I have a method with a signature like `def process_request(self, action:SomeClass.FromDict)` which takes a dictionary for the `action` parameter and passes that to SomeClass.FromDict which then returns a instance of `SomeClass`.

In another case, when dealing with Twisted in Python3 and that all strings are type `` I used something like the magic_decorator above and a transformer `SafeStr` (ex. def do_something(name:SafeStr)` to ensure that the name parameter is ALWAYS of type str. Anecdotally Python3 blows up if you try to do something like .startswith()`.

Grand scheme I think this is an interesting quirk but if my comments and wording isn’t clear, I would prescribe caution if using this in revenue generating code (or code intended to make you wealthy or at least provide money for pizza & beer).

I needed the pathlib equivalent to os.walk so I went to the source code for os.walk and reimplemented it to use pathlib instead

def path_walk(top, topdown = False, followlinks = False):
    """
         See Python docs for os.walk, exact same behavior but it yields Path() instances instead
    """
    names = list(top.iterdir())

    dirs = (node for node in names if node.is_dir() is True)
    nondirs =(node for node in names if node.is_dir() is False)

    if topdown:
        yield top, dirs, nondirs

    for name in dirs:
        if followlinks or name.is_symlink() is False:
            for x in path_walk(name, topdown, followlinks):
                yield x

    if topdown is not True:
        yield top, dirs, nondirs

yes there is Path.glob(“**”) but I like how os.walk is structured and this passes my unit-tests.

dirs and nondirs are generators out of habit. List comprehensions would likely be better and it’s almost impossible to avoid the overhead memory cost so having them as is, is just personal preference.