Python zipfile module doesn’t compress files

I have a problem with compression in Python. I know I should call the ZIP_DEFLATED method when writing to make the zip file compressed, but it does not work for me. I have 3 PDF documents in the C:zip directory. When I run the following code it works just fine:

import os,sys
list = os.listdir('C:zip')
file = ZipFile('test.zip','w')
for item in list:
    file.write(item)
file.close()

It makes the test.zip file without the compression. When I change the fourth row to this:

file = ZipFile('test.zip','w', compression = ZIP_DEFLATED)

It also makes the test.zip file without the compression. I also tried to change the write method to give it the compress_ type argument:

file.write(item, compress_type = ZIP_DEFLATED)

But that doesn’t work either. I use Python version 2.7.4 with Win7. I tired the code with another computer (same circumstances, Win7 and Python 2.7.4), and it made the test.zip file compressed just like it should. I know the zlib module should be available, when I run this:

import zlib

It doesn’t return an error, also if there would be something wrong with the zlib module the code at the top should had return an error too, so I suspect that zlib isn’t the problem.

Answer

By default the ZIP module only store data, to compress it you can do this:

import zipfile
try:
    import zlib
    mode= zipfile.ZIP_DEFLATED
except:
    mode= zipfile.ZIP_STORED

zip= zipfile.ZipFile('zipfilename', 'w', mode)
zip.write(item)
zip.close()

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Answer