Writing to file in python finishes only when manually stopping the program

Question

I have a simple program that writes to a file in a for loop (30k+ iterations). I noticed that the program is taking abnormally long to finish, after which I decided to kill it. The file it is writing to has 29900 lines created withing 30s and the remaining 100 are not written - the program doesn't exit and it takes hours to do so.

Once I killed it, it finished writing the remaining 100 or so lines.

f1 = open('parts.txt', "w") for line in lines: category = line[2] f1.write(category + '\n') print('------- done -------') f1.close()

Is there anything obvious that I am missing?

Error - you have unmatched " and ' and ) - so this is not your real code. Please fix and give us a correct minimal reproducible example. Thanks — Patrick Artner
– Patrick Artner, Commented Oct 17, 2019 at 13:31
It is not my real code, because the file parts.txt is too large to post here. Rerunning and reproducing the code here is not necessary - my usage of files may be wrong. — oneiros
– oneiros, Commented Oct 17, 2019 at 13:35

BramAppel · Accepted Answer · 2019-10-17 13:30:39Z

1

Use a with statement, this way the file is always closed independent of the exit status.

with open('parts.txt', 'w') as fw: for line in lines: category = line[2] fw.write(category + '\n') print('----- done ------')

answered Oct 17, 2019 at 13:30

BramAppel

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5 Comments

oneiros Over a year ago

The explicit fw.close() is not needed?

Patrick Artner Over a year ago

while a sound advice this answer is premature - the only error the OP code shows is SyntaxError: EOL while scanning string literal because it is not valid python.

BramAppel Over a year ago

@oneiros nope, this is called implicitly when the with block is exited.

r.ook Over a year ago

@oneiros look up the with statement context manager

oneiros Over a year ago

@Krrr - will do. Thank for the post - I am somewhat new to the language and this is a concept I need to understand.

Piklet · Accepted Answer · 2023-10-19 00:34:12Z

I spent a while trying to figure out why this was happening to me - it turns out it wasn't my Python code's fault at all for me: my IDE (PyCharm) doesn't seem to refresh (or at least often) the file tree whilst the program is running. However, the files were still generated, and looking at the file explorer/finder (or unfocusing/refocusing PyCharm), the files were generated.

I know this wasn't the answer for OP, but for anyone else who's having issues down the line (and searching around and comes across this) and nothing done in Python seems to work - check if the file has been generated with your system's file browser!

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