Should you always use with when printing to files in python

Question

From what I have seen, there are 2 ways to print to a file:

Method 1

file = open('myfile.txt', 'a')
file.write('sup')

# LATER ON

file.write('yo')

# AT THE END

file.close()

Method 2

with open('myfile.txt', 'a') as f:
   f.write('sup')

# LATER ON

with open('myfile.txt', 'a') as f:
   f.write('yo')

The problem with the first method, is that if the program were to end abruptly, the file does not close and is not saved. Because of this, I am currently using with and reopening the file everytime I want to print to it. However, I realize this may be a bad idea considering that I append to this file almost every 5 seconds. Is there a major performance hit in reopening the file with "with" before printing every time? And if so, how should I handle abrupt endings that result in the file not being closed using the first method.

See this: http://stackoverflow.com/questions/19711344/why-is-with-open-better-for-opening-files-in-python — Sharif Mamun, Mar 10 '14 at 02:55
Option three: A single `with` covering both sets of writes. No reason to dedent after the first `f.write()`. — Steven Rumbalski, Mar 10 '14 at 03:25
In short, yes, there is a performance penalty for open and closing the file in the context manager. But it is on the order of microseconds, and will be negligible if you are only writing to the file every second or so. — jme, Mar 10 '14 at 04:18

metatoaster · Accepted Answer · 2014-03-10T03:08:05.870

0

In the first method, what you want to do is to flush your changes to the file system after you are done with a set of writes. i.e.:

file.flush()

For something simple like what you had in your example, yes you should use with open... for interacting with files.

edited Mar 10 '14 at 03:08

answered Mar 10 '14 at 02:51

metatoaster

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Seems to me flushing would be much cheaper in terms of resources, and will work just as effectively. – holdenweb Mar 10 '14 at 03:34
+1 Use just one `with open ...`, but call `f.flush()` at "important" points. – Jonathon Reinhart Mar 11 '14 at 04:23

score -3 · Answer 2 · answered Mar 10 '14 at 02:49

-3

I would recommend that you place your write operations inside a try: and your close in an finally:

with open('myfile.txt', 'a') as f:
    try:
        f.write('sup')
        # Extra Code
        f.write('yo')
    finally:
        f.close()

This ensures that f. will close properly if there is an error or if your a simply done running.

This is part of pythons cleanup functions

answered Mar 10 '14 at 02:49

secumind

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The context manager already calls close properly; the whole point of wrapping this in a contextmanager is to avoid writing extra file object handling code. Replace `# Extra Code` with `raise Exception` and sup will be written into myfile.txt with or without the try.. finally block. – metatoaster Mar 10 '14 at 02:53

Should you always use with when printing to files in python

2 Answers2