for line in open(filename)

Question

I frequently see python code similar to

for line in open(filename):
    do_something(line)

When does filename get closed with this code?

Answer 1

python is garbage-collected - cpython has reference counting and a backup cycle detecting garbage collector.

File objects close their file handle when the are deleted/finalized.

Thus the file will be eventually closed, and in cpython will closed as soon as the for loop finishes.