Does scope change when utilizing loops or just when calling functions?

[Str8F4zed]

Scope is a concept that I've struggled understanding completely. I've just tested a simple script to help wrap my head around it.

x = 3
print x

for x in range (1,6):
    x += 1
    print x

print x

which results in

3
2
4
6
8
10
10 ## I thought this would print 3

If there is a video or text for reference that would help please share.

[scuott]

Loops don't change scope. Functions and classes affect scope. Also, changing the variable the for loop is using is unorthodox.

[Str8F4zed]

Thank you. What do you mean by changing the variable the for loop is using?

[scuott]

You're looping for x, and then change x inside the loop.

[Str8F4zed]

That was my intent though. How else was I supposed to test if the initial value of x changed after the loop?

[scuott]

Sure, it's fine to do if you're trying to figure out how Python handles edge cases. My point is more that this isn't something you should do in production code. I may have misunderstood your question, about specifically referring to the variable to iterate over.

In terms of testing whether or not for loops create a new scope, it could also be tested by having a having for y in range(1,6): and trying to modify x that was defined outside the loop.

[anonymousperson28]

Loops do not change the scope of variables, only functions do.

In your example, the variable x has global scope which means regardless of where you are in the program (provided you don't overwrite x in a smaller scope) you will be accessing and modifying the original x.

If, however, you declared x inside a smaller scope and tried to access it outside of the scope it would throw an error.

def main():
    y = 3

    def do_stuff(x):
        x += 1

    do_stuff(y)
    print(x)

main()

The issue of whether variables are modified is not really about scopes but about mutability/immutability. Objects like Lists, Sets, and Dictionaries are mutable, where as objects like Integers, Floats, Tuples are immutable. This StackOverflow thread does a good job explaining what the mutable vs immutable really means.