How many times does a for loop evaluate its expression list?

Question

I have the following code:

list1 = [4,1,2,6]
for elem in sorted(list1):
    #some task

I was wondering how many times does Python sort the

Answer 1

In both code examples, the list is sorted only once.

The expression on the right of the in operator in a for-loop header is evaluated just once, before looping commences. You can read about this in the documentation:

for_stmt ::=  "for" target_list "in" expression_list ":" suite
              ["else" ":" suite]

The expression list is evaluated once; it should yield an iterable object.

In fact, the second code example is less efficient because there is an unnecessary assignment.