The gzip Module
The gzip module allows you to read and write gzip-compressed files as if they were ordinary files, as shown in Example 5-24.
Example 5-24. Using the gzip Module to Read a Compressed File
File: gzip-example-1.py import gzip file = gzip.GzipFile("samples/sample.gz") print file.read() Well it certainly looks as though we're in for a splendid afternoon's sport in this the 127th Upperclass Twit of the Year Show.
The standard implementation doesn't support the seek and tell methods. Example 5-25 shows how to add forward seeking.
Example 5-25. Extending the gzip Module to Support seek/tell
File: gzip-example-2.py
import gzip
class gzipFile(gzip.GzipFile):
# adds seek/tell support to GzipFile
offset = 0
def read(self, size=None):
data = gzip.GzipFile.read(self, size)
self.offset = self.offset + len(data)
return data
def seek(self, offset, whence=0):
# figure out new position (we can only seek forwards)
if whence == 0:
position = offset
elif whence == 1:
position = self.offset + offset
else:
raise IOError, "Illegal argument"
if position < self.offset:
raise IOError, "Cannot seek backwards"
# skip forward, in 16k blocks
while position > self.offset:
if not self.read(min(position - self.offset, 16384)):
break
def tell(self):
return self.offset
#
# try it
file = gzipFile("samples/sample.gz")
file.seek(80)
print file.read()
this the 127th
Upperclass Twit of the Year Show.
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