CODEWITHSUNDEEP
python-3.xperformancefor-loopiterableis-empty
NebelFox
NebelFox

Reputation: 25

Checking if iterable is empty before while loop

Recently I have had to make dynamically changing lists I iterate through in the main loop. But they are empty initially, and may be empty sometimes. Here are two cases:

# The first one
iterable = []
if iterable:
    for i in iterable:
        # do sth

# and the second
iterable = []
for i in iterable:
    # do sth

I'm wondering if there is some difference in performance of these 2 cases, or the empty check is already implemented in the for loop?

Upvotes: 1

Views: 1736

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 627065

When you iterate over a define list variable, you do not encounter any problems, have a look:

>>> iterable=[]
>>> for x in iterable:
    print(x)

>>>

The empty check is done automatically for you.

So, it is preferable to use the second code snippet in your question, because there is no redundant if iterable: code line.

Upvotes: 1

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