Is Using List Comprehensions for Side Effects in Python Considered Pythonic?

List Comprehensions for Side Effects: A Pythonic Approach

In Python, list comprehensions are often used to create new lists from existing sequences. However, it can be tempting to use list comprehensions for their side effects, such as printing to the screen or updating a graphical user interface.

Consider the following function, which performs side effects but does not return any meaningful values:

def fun_with_side_effects(x):
    # ...side effects...
    return None

The question arises: is it Pythonic to call this function using list comprehensions?

[fun_with_side_effects(x) for x in y if (...conditions...)]

Alternatively, one could call the function using a standard for loop:

for x in y:
    if (...conditions...):
        fun_with_side_effects(x)

While list comprehensions may seem like a concise and efficient solution, they are considered anti-Pythonic in this context. This is because the intermediate list is created and then discarded immediately after, which can be both wasteful and computationally expensive, especially if the sequence is large.

The for loop approach is more Pythonic as it avoids the creation of an unnecessary list. It is also more efficient, as it only calls fun_with_side_effects when necessary.

Therefore, it is recommended to use the for loop syntax when calling functions with side effects. This approach adheres to Pythonic principles and ensures code efficiency.

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