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Fastest way to write data into a file using Python?

0 votes
2,630 views

I need to write into a file for a project which will be evaluated on the basis of time. What is the fastest way to write 200 Mb of data, accumulated as a list into a file.

Presently I am using this:

with open('index.txt','w') as f:
 f.write("".join(data))
 f.close()

where data is a list of strings which I want to dump into the index.txt file

posted Jan 14, 2014 by Luv Kumar

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1 Answer

+1 vote 
with open('index.txt','w') as f:
 for hunk in data:
 f.write(hunk)

You don't need to f.close() - that's what the 'with' block guarantees. Iterating over data and writing each block separately means you don't have to first build up a 200MB string. After that, your performance is going to be mainly tied to the speed of your disk, not anything that Python can affect.

answer Jan 14, 2014 by Mandeep Sehgal
Thanks for the tip on the closing of the file. I did not know that with ensures closing of the file after iteration is over.

Which is more fast?
Creating a 200 Mb string and then dumping into a file or dividing the 200 Mb string into chunks and then writing those chunks. Won't writing the chunks call more i/o operation?
commented Jan 14, 2014 by anonymous
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