Oftentimes, we call functions over a wide range of parameter values, e.g. to generate plots for different scenarios. For multiple parameters, this leads to ugly multi-loops and cumbersome boilerplate. With this snippet it becomes one line.

product_call.py

from typing import Callable, Optional, Dict, Any
import itertools
from tqdm.auto import tqdm

def product_call(
        fct: Callable,
        static: Optional[Dict[str, Any]] = None,
        multi: Optional[Dict[str, Any]] = None,
        progress=False
) -> Tuple[List[Dict[str, Any]], List[Any]]:
    """ Execute the same function multiple times, where we change parameters
    in each call.

    Kilian Lieret 2019
    https://gist.github.com/klieret/0f3b1b8a0b9b143702ae1aa662264029

    Example:

        multiplex(fct, multi=dict(a=[1, 2, 3]), static=dict(b=4))

    Will call

        fct(a=1, b=4)
        fct(a=2, b=4)
        fct(a=3, b=4)

    If a value for one of the static arguments is a string, we will try to
    format it with the multi arguments, e.g. static=dict(b="{a}.pdf")
    will result in

        fct(a=1, b="1.pdf")
        fct(a=2, b="2.pdf")
        fct(a=3, b="3.pdf")

    Args:
        fct: The function to call
        static: Dictionary of keyword arguments that are passed to the function
            (but that do not chanage for each call)
        multi: Dictionary of keyword arguments to lists of values, that are
            passed to the function (see above)
        progress: Use tqdm to draw a nice progress bar (default False)

    Returns:
        list of kwarg dictionaries and list of corresponding results.
    """
    if static is None:
        static = {}
    if multi is None:
        multi = {}
    keys = list(multi.keys())
    values = [multi[key] for key in keys]  # Ordered!
    products = list(itertools.product(*values))
    if progress:
        products = tqdm(progress)
    results = []
    kwargs_list = []

    class FormatDefaultDict(dict):
        def __missing__(self, key):
            return '{' + key + '}'

    for setting in products:
        multi_kwargs = {keys[i]: setting[i] for i in range(len(keys))}
        static_kwargs = {}
        for key, value in static.items():
            if isinstance(value, str):
                value = value.format_map(FormatDefaultDict(multi_kwargs))
            static_kwargs[key] = value
        kwargs = {**multi_kwargs, **static_kwargs}
        res = fct(**kwargs)
        results.append(res)
        kwargs_list.append(kwargs)
    return kwargs_list, results


def test_product_call():
    def _test(a, b, c):
        return a + b

    kwargs, values = product_call(
        _test,
        static=dict(c="{a}{b}"),
        multi=dict(a=[1, 2, 3], b=[4, 5, 6])
    )
    assert kwargs == [
        {'a': 1, 'b': 4, 'c': '14'},
        {'a': 1, 'b': 5, 'c': '15'},
        {'a': 1, 'b': 6, 'c': '16'},
        {'a': 2, 'b': 4, 'c': '24'},
        {'a': 2, 'b': 5, 'c': '25'},
        {'a': 2, 'b': 6, 'c': '26'},
        {'a': 3, 'b': 4, 'c': '34'},
        {'a': 3, 'b': 5, 'c': '35'},
        {'a': 3, 'b': 6, 'c': '36'}
    ]
    assert values == [5, 6, 7, 6, 7, 8, 7, 8, 9]