reading tar file contents without untarring it, in python script

Question

I have a tar file which has number of files within it. I need to write a python script which will read the contents of the files and gives the count o total characters, including total number of letters, spaces, newline characters, everything, without untarring the tar file.

Answer 1

you can use getmembers()

>>> import  tarfile
>>> tar = tarfile.open("test.tar")
>>> tar.getmembers()

After that, you can use extractfile() to extract the members as file object. Just an example

import tarfile,os
import sys
os.chdir("/tmp/foo")
tar = tarfile.open("test.tar")
for member in tar.getmembers():
    f=tar.extractfile(member)
    content=f.read()
    print "%s has %d newlines" %(member, content.count("\n"))
    print "%s has %d spaces" % (member,content.count(" "))
    print "%s has %d characters" % (member, len(content))
    sys.exit()
tar.close()

With the file object "f" in the above example, you can use read(), readlines() etc.

Answer 2

you need to use the tarfile module. Specifically, you use an instance of the class TarFile to access the file, and then access the names with TarFile.getnames()

 |  getnames(self)
 |      Return the members of the archive as a list of their names. It has
 |      the same order as the list returned by getmembers().

If instead you want to read the content, then you use this method

 |  extractfile(self, member)
 |      Extract a member from the archive as a file object. `member' may be
 |      a filename or a TarInfo object. If `member' is a regular file, a
 |      file-like object is returned. If `member' is a link, a file-like
 |      object is constructed from the link's target. If `member' is none of
 |      the above, None is returned.
 |      The file-like object is read-only and provides the following
 |      methods: read(), readline(), readlines(), seek() and tell()

Answer 3

An implementation of the methods mentioned by @stefano-borini Access a tar archives member via file name like so

#python3
myFile = myArchive.extractfile( 
    dict(zip(
        myArchive.getnames(), 
        myArchive.getmembers()
    ))['path/to/file'] 
).read()`

Credits:

• dict(zip( from https://stackoverflow.com/a/209854/1695680
• tarfile.getnames from https://stackoverflow.com/a/2018523/1695680
• Additionally, for my uses, reading a tar archive from buffer How to construct a TarFile object in memory from byte buffer in Python 3?