Python, difference between 'open' and 'with open'

Question

I have not used the with statement, but am somewhat familiar with its purpose. With the follow code, the #1 block works as expected, but #2 -- which, correct me here, should do the same thing as the first one -- throws the following exception FileExistsError: [Errno 17] File exists: 'mydir'.

import os

if not(os.path.exists('mydir')):
    os.makedirs('mydir')

path = 'mydir'
filename = 'msg.txt'
filename2 = 'msg2.txt'

#1
with open(os.path.join(path, filename), 'w') as temp_file:
    temp_file.write("hello")

#2
temp_file = open(os.path.join(path, filename2), 'w')
temp_file.write("hello again")
temp_file.close()

See this http://stackoverflow.com/questions/3012488/what-is-the-python-with-statement-designed-for — intboolstring, Dec 23 '15 at 06:03
I cannot reproduce your problem. Your script works as expected. — Mike Müller, Dec 23 '15 at 06:03
The exception doesn't appear to have anything to do with the use or not of `with`, but rather with the filenames you're using. — Blckknght, Dec 23 '15 at 06:04
I am on Mac OS X. There should be no difference, even on Windows. — Mike Müller, Dec 23 '15 at 06:05
In your original post you used `os.path.exists('teams')` not `os.path.exists('mydir')`. Likely this was the reason. — Mike Müller, Dec 23 '15 at 06:08

score 9 · Answer 1 · edited May 23 '17 at 10:30

Part 1: The Difference Between open and with open

Basically, using with just ensures that you don't forget to close() the file, making it safer/preventing memory issues.

Part 2: The FileExistsError

This is an OS error and, therefore, may be OS specific. Your syntax is correct though, assuming that you want to overwrite (truncate) the previous file.

This is probably why the problem is OS-specific and most other users are unable to duplicate the issue.

However, if it's causing issues, you could try using w+ mode and it may fix the issue.

A similar issue was documented here.

EDIT: I just noticed the comment stream about teams originally being the path. Glad it got fixed!

Mike Müller · Accepted Answer · 2015-12-23T06:54:57.400

This error was caused by a previous version of the posted script. It looked like this:

if not(os.path.exists('teams')):
    os.makedirs('mydir')

This tests for the existence of the directory teams but tries to create a new directory mydir.

Suggested solution: use variable names for everything, don't hardwire strings for paths:

path = 'mydir'

if not(os.path.exists(path)):
    os.makedirs(path)

And yes, both #1 and #2 do essentially the same. But the with statement also closes the file in case of an exception during writing.

Python, difference between 'open' and 'with open'

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