python closing file when using in-line "for" statement

Question

I am counting the lines in a file using the following:

n = sum(1 for line in open(counts_file_location))

Questions:

does the file counts_file_location gets closed automatically at the end of "for" loop?
if the file does not get closed automatically, how do I close it? There is no file_pointer assigned to to the file.

Possible duplicate of [Is explicitly closing files important?](http://stackoverflow.com/questions/7395542/is-explicitly-closing-files-important) — Patrick Kostjens, Mar 10 '17 at 21:44
Possible duplicate of [How to get line count cheaply in Python?](http://stackoverflow.com/questions/845058/how-to-get-line-count-cheaply-in-python) — dot.Py, Mar 10 '17 at 21:44
Just don't open files this way. Use a `with` statement. It's much safer, especially on Python implementations that aren't CPython. — user2357112, Mar 10 '17 at 21:44

Yang · Answer 1 · 2017-03-10T22:29:12.223

1

It should, but it is implementation dependent

If you want to make sure the file gets closed, try with open:

with open(counts_file_location) as file:
    n = sum(1 for line in file)

edited Mar 10 '17 at 22:29

answered Mar 10 '17 at 21:44

Yang

This isn't addressed to the specific question -- you mean `n = sum(1 for line in file)` – Denziloe Mar 10 '17 at 22:14

Neil · Answer 2 · 2017-03-10T22:11:45.207

0

Here's a single line to open the file, close the file, and get the number of lines:

lineCount = (lambda a: (sum(1 for line in a), a.close()))(open(counts_file_location))[0]

edited Mar 10 '17 at 22:11

answered Mar 10 '17 at 21:59

Neil

score 0 · Answer 3 · answered Mar 10 '17 at 22:06

0

count = 0
with open(counts_file_location) as my_file:
  for line in my_file:
    count += 1
print count

It's not a one-liner, but it's readable, works fine and closes the file.

If you need it often, you could define the corresponding function.

answered Mar 10 '17 at 22:06

Eric Duminil

3 Answers3