map multiple functions to a single input

Question

map is a builtin function that takes one function func and one or more iterables, and maps the function to each element in the iterables. I wrote the following function that does the reverse, but it feels like this is such a basic operation that someone must have done this before, and hopefully given a better name to this.

This appears to be a related question with a slightly different solution:

https://stackoverflow.com/questions/35858735/apply-multiple-functions-with-map

from toolz import curry, compose


@curry
def fmap(funcs, x):
    return (f(x) for f in funcs)


cases = fmap([str.upper, str.lower, str.title])
tuple_of_cases = compose(tuple, cases)
strings = ['foo', 'bar', 'baz']
list(map(tuple_of_cases, strings))

mcocdawc · Accepted Answer · 2021-07-08 15:09:41Z

First and foremost, the code is not working as posted. One has to add from toolz import curry, compose.

Apart from this I like the solution and striving for more functional programming is probably always better. I also don't know a canonical solution for passing an argument to functions in python

Things I would definitely change:

I would not overdo the functional programming syntax. list(map(...)) should be IMHO written as list comprehension. Even if one does not cast the result of map to a list, I find a generator comprehension to be more readable.

Small stuff:

fmap could get a docstring.
Type information with mypy etc. would be nice.
Perhaps through would be a better name for fmap. At least if one peeks to other languages. (https://reference.wolfram.com/language/ref/Through.html)
Since strings is a constant, it could become uppercase.
Sometimes stuff does not need a separate name if functions are just concatenated and IMHO tuple_of_cases can go.

from toolz import curry, compose


@curry
def fmap(funcs, x):
    return (f(x) for f in funcs)

STRINGS = ['foo', 'bar', 'baz']
cases = compose(tuple, fmap([str.upper, str.lower, str.title]))

[cases(x) for x in STRINGS]

I fixed the missing import in my question. I couldn't really find a suitable name for the concept, but I like through, thanks for pointing me in that direction. — hugovdberg
– hugovdberg, Commented Jul 8, 2021 at 15:17

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