access scope of variable in for loop

Question

I have searched the SO before I post this question here and hopefully this is not a duplicated one.

def print_me():
    a_list = range(1, 10)
    for idx, aa in enumerate(a_list):
        pass
    print(idx)

if __name__ == '__main__' : print_me()

Output is as follows:

8

I came from C++ world and could not figure out why idx is still in the scope when the code is out side of for loop?

Thank you

Community · Accepted Answer · 2017-05-23 10:34:30Z

10

for loop doesn't create any scope. This is the reason.

In this particular code idx is a local variable of the print_me function.

From the docs:

The following are blocks:

a module
a function body
a class definition

Update

Generator expressions have their own scopes too.

As of Python 3.0 list comprehensions also have their own scopes.

edited May 23, 2017 at 10:34

CommunityBot

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answered Oct 10, 2011 at 15:46

ovgolovin

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3 Comments

user395760 Over a year ago

In fact, only very few language constructs create scopes. There's only module scope, class scope and function scope, and that's about it.

kindall Over a year ago

List comprehensions also have their own scopes. Well, any comprehension or generator expression.

max Over a year ago

Anyone knows why Python doesn't create a scope for for / while loops? Is there any benefit to having those variables present later? (The disadvantage is clearly namespace pollution, hence more bugs.)

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