writing to file from cython

Question

By profiling, I've determined that about 60% of my program's time is spent in writing to file, in the one line:

fout.write('%d\t%d\n' % (i, j))

Here i and j are integers. Two questions: would implementing this in Cython give me a significant speed gain, and how would I implement it in Cython? I'm having trouble finding examples of writing to files from Cython.

Regarding the last point, this line occurs in a function that is called by the rest of my program very often to dump output to a file, so I'd like to leave the file open between function calls, and pass in a file object rather than reopening the file in each call.

String formatting: `tmp = '%d\t%d\n' % (i, j)` and writing to file `fout.write(tmp)` are two separate statements. You may need to re-profile. — iljau, Feb 12 '14 at 01:52
[see this answer](http://stackoverflow.com/a/4961701/1797098) — embert, Feb 12 '14 at 16:53

Saullo G. P. Castro · Accepted Answer · 2018-03-23T11:23:56.783

2

You can get a significant performance gain by sending to your hard drive a compacted amount of data, which can be achieved using numpy.savez_compressed(), or writting in binary format:

with open('name.output', 'wb') as fout:
    fout.write(data)

Cython uses the same functions to write files that Python does, accessed through the Python API, and therefore it should not make it faster.

edited Mar 23 '18 at 11:23

answered May 27 '14 at 09:18

Saullo G. P. Castro

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I have a [Cython post](http://stackoverflow.com/questions/41944883/verifying-compatibility-in-compiling-extension-types-and-using-them-with-cdef) you may be able to provide insight on. – ballade4op52 Jan 31 '17 at 20:49
Thanks, I'll check it out... Just had a quick look – Saullo G. P. Castro Jan 31 '17 at 23:55
An update has been made outlining the bulk that needed resolving. Thank you anyway. – ballade4op52 Feb 01 '17 at 00:07

writing to file from cython

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