EarlyReturn

Communicate to Modify and Sequence to stop function-execution and return the value given to EarlyReturn.

Does not work for Assert.

Example

The example

from some_package import load_fct, save_fct
from typing_exe.early_return import EarlyReturn
from typing_exe.annotations import Modify
from typing_exe.decorators import execute_annotations


def load_img(a: str):
    filename = a.split(".")[:-1]
    fileformat = a.split(".")[-1]

    if fileformat == "pdf":
        # a was already sharpened and was saved as a pdf-file 
        #   -> sharpen_img should simply return the loaded data
        pdf = load_fct(a)
        return EarlyReturn(pdf)

    # Load the image and give it and the filename to sharpen_img
    image = load_fct(a, fileformat=fileformat)
    return filename, image


@execute_annotations
def sharpen_img(a: Modify[str, load_img]):
    filename, image = *a
    # Sharpen the image here 
    image = ... 
    # Save the result
    save_fct(filename + ".pdf", image)
    # Return sharpened image
    return image

Explanation

The function sharpen_img is used to load an image from a file given by name. It loads the image in load_img—executed in Modify—sharpens it, saves it as a PDF-file, and then returns the sharpened image.

If the file given to it is already in PDF-format, that means that it has already been sharpened and so load_img loads it and returns an EarlyReturn of the loaded, sharpened image. The function-body of sharpen_img will not be executed; instead, the sharpened image will be returned immediately.

EarlyReturn for default parameters

EarlyReturn can even be used as a default value! This way, if a parameter to a function is unfilled, a default can be returned immediately.

from typing import Union
from typing_exe.early_return import EarlyReturn
from typing_exe.decorators import execute_annotations


@execute_annotations
def foo(a: Union[str, EarlyReturn] = EarlyReturn("well that was quick")):
    ...

If you are using type-checkers, EarlyReturn of course has to be allowed as a type to the parameter, as seen in the example above.

EarlyReturn

• returns The value that should be returned early