Is it Pythonic to use list comprehensions for just side effects?

Question

Think about a function that I\'m calling for its side effects, not return values (like printing to screen, updating GUI, printing to a file, etc.).

def fun_wi         


        

Answer 1

Using a list comprehension for its side effects is ugly, non-Pythonic, inefficient, and I wouldn't do it. I would use a for loop instead, because a for loop signals a procedural style in which side-effects are important.

But, if you absolutely insist on using a list comprehension for its side effects, you should avoid the inefficiency by using a generator expression instead. If you absolutely insist on this style, do one of these two:

any(fun_with_side_effects(x) and False for x in y if (...conditions...))

or:

all(fun_with_side_effects(x) or True for x in y if (...conditions...))

These are generator expressions, and they do not generate a random list that gets tossed out. I think the all form is perhaps slightly more clear, though I think both of them are confusing and shouldn't be used.

I think this is ugly and I wouldn't actually do it in code. But if you insist on implementing your loops in this fashion, that's how I would do it.

I tend to feel that list comprehensions and their ilk should signal an attempt to use something at least faintly resembling a functional style. Putting things with side effects that break that assumption will cause people to have to read your code more carefully, and I think that's a bad thing.