Problem with zipfile and newlines

[Neil Crighton]

I'm using the zipfile library to read a zip file in Windows, and it
seems to be adding too many newlines to extracted files. I've found
that for extracted text-encoded files, removing all instances of '\r'
in the extracted file seems to fix the problem, but I can't find an
easy solution for binary files.

The code I'm using is something like:

from zipfile import Zipfile
z = Zipfile(open('zippedfile.zip'))
extractedfile = z.read('filename_in_zippedfile')

I'm using Python version 2.5. Has anyone else had this problem
before, or know how to fix it?

Thanks,

Neil

 

[John Machin]

I'm using the zipfile library to read a zip file in Windows, and it
seems to be adding too many newlines to extracted files. I've found
that for extracted text-encoded files, removing all instances of '\r'
in the extracted file seems to fix the problem, but I can't find an
easy solution for binary files.

The code I'm using is something like:

from zipfile import Zipfile
z = Zipfile(open('zippedfile.zip'))
extractedfile = z.read('filename_in_zippedfile')

"Too many newlines" is fixed by removing all instances of '\r'. What
are you calling a newline? '\r'??

How do you know there are too many thingies? What operating system
were the original files created on?

When you do:
# using a more meaningful name
extractedfilecontents = z.read('filename_in_zippedfile')
then:
print repr(extractedfilecontents)
what do you see at the end of what you regard as each line:
(1) \n
(2) \r\n
(3) \r
(4) something else
?

Do you fiddle with extractedfilecontents (other than trying to fix it)
before writing it to the file?

When you write out a text file,
do you do:
open('foo.txt', 'w').write(extractedfilecontents)
or
open('foo.txt', 'wb').write(extractedfilecontents)
?

When you write out a binary file,
do you do:
open('foo.txt', 'w').write(extractedfilecontents)
or
open('foo.txt', 'wb').write(extractedfilecontents)
?

 

[Duncan Booth]

I'm using the zipfile library to read a zip file in Windows, and it
seems to be adding too many newlines to extracted files. I've found
that for extracted text-encoded files, removing all instances of '\r'
in the extracted file seems to fix the problem, but I can't find an
easy solution for binary files.

The code I'm using is something like:

from zipfile import Zipfile
z = Zipfile(open('zippedfile.zip'))
extractedfile = z.read('filename_in_zippedfile')

I'm using Python version 2.5. Has anyone else had this problem
before, or know how to fix it?

Thanks,

Zip files aren't text. Try opening the zipfile file in binary mode:

open('zippedfile.zip', 'rb')

 

[John Machin]

Zip files aren't text. Try opening the zipfile file in binary mode:

open('zippedfile.zip', 'rb')

Good pickup, but that indicates that the OP may have *TWO* problems,
the first of which is not posting the code that was actually executed.

If the OP actually executed the code that he posted, it is highly
likely to have died in a hole long before it got to the z.read()
stage, e.g.
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\python25\lib\zipfile.py", line 346, in __init__
self._GetContents()
File "C:\python25\lib\zipfile.py", line 366, in _GetContents
self._RealGetContents()
File "C:\python25\lib\zipfile.py", line 404, in _RealGetContents
centdir = struct.unpack(structCentralDir, centdir)
File "C:\python25\lib\struct.py", line 87, in unpack
return o.unpack(s)
struct.error: unpack requires a string argument of length 46
If it somehow made it through the open stage, it surely would have
blown up at the read stage, when trying to decompress a contained
file.

Cheers,
John

 

[neilcrighton]

Sorry my initial post was muddled. Let me try again.

I've got a zipped archive that I can extract files from with my
standard archive unzipping program, 7-zip. I'd like to extract the
files in python via the zipfile module. However, when I extract the
file from the archive with ZipFile.read(), it isn't the same as the 7-
zip-extracted file. For text files, the zipfile-extracted version has
'\r\n' everywhere the 7-zip-extracted file only has '\n'. I haven't
tried comparing binary files via the two extraction methods yet.

Regarding the code I posted; I was writing it from memory, and made a
mistake. I didn't use:

z = zipfile.ZipFile(open('foo.zip', 'r'))

I used this:

z = zipfile.ZipFile('foo.zip')

But Duncan's comment was useful, as I generally only ever work with
text files, and I didn't realise you have to use 'rb' or 'wb' options
when reading and writing binary files.

To answer John's questions - I was calling '\r' a newline. I should
have said carriage return. I'm not sure what operating system the
original zip file was created on. I didn't fiddle with the extracted
file contents, other than replacing '\r' with ''. I wrote out all the
files with open('outputfile','w') - I seems that I should have been
using 'wb' when writing out the binary files.

Thanks for the quick responses - any ideas why the zipfile-extracted
files and 7-zip-extracted files are different?

 

[neilcrighton]

I think I've worked it out after reading the 'Binary mode for files'
section of http://zephyrfalcon.org/labs/python_pitfalls.html

zipfile extracts as file as a binary series of characters, and I'm
writing out this binary file as a text file with open('foo','w').
Normally Python converts a '\n' in a text file to whatever the
platform-dependent indication of a new line is ('\n' on Unix, '\r\n'
on Windows, '\r' on Macs). So it sees '\r\n' in the binary file and
converts it to '\r\r\n' for the text file.

The upshot of this is that writing out the zipfile-extracted files
with open('foo','wb') instead of open('foo','w') solves my problem.