Constructor for the GzipFile class, which simulates most of the
methods of a file object, with the exception of the truncate()
method. At least one of fileobj and filename must be given a non-trivial
value.
The new class instance is based on fileobj, which can be a regular file, an
io.BytesIO object, or any other object which simulates a file. It
defaults to None, in which case filename is opened to provide a file
object.
When fileobj is not None, the filename argument is only used to be
included in the gzip file header, which may include the original
filename of the uncompressed file. It defaults to the filename of fileobj, if
discernible; otherwise, it defaults to the empty string, and in this case the
original filename is not included in the header.
The mode argument can be any of 'r', 'rb', 'a', 'ab', 'w',
'wb', 'x', or 'xb', depending on whether the file will be read or
written. The default is the mode of fileobj if discernible; otherwise, the
default is 'rb'.
Note that the file is always opened in binary mode. To open a compressed file
in text mode, use open() (or wrap your GzipFile with an
io.TextIOWrapper).
The compresslevel argument is an integer from 0 to 9 controlling
the level of compression; 1 is fastest and produces the least
compression, and 9 is slowest and produces the most compression. 0
is no compression. The default is 9.
The mtime argument is an optional numeric timestamp to be written to
the last modification time field in the stream when compressing. It
should only be provided in compression mode. If omitted or None, the
current time is used. See the mtime attribute for more details.
Calling a GzipFile object’s close() method does not close
fileobj, since you might wish to append more material after the compressed
data. This also allows you to pass an io.BytesIO object opened for
writing as fileobj, and retrieve the resulting memory buffer using the
io.BytesIO object’s getvalue() method.
GzipFile supports the io.BufferedIOBase interface,
including iteration and the with statement. Only the
truncate() method isn’t implemented.
GzipFile also provides the following method and attribute:
-
peek(n)
Read n uncompressed bytes without advancing the file position.
At most one single read on the compressed stream is done to satisfy
the call. The number of bytes returned may be more or less than
requested.
Note
While calling peek() does not change the file position of
the GzipFile, it may change the position of the underlying
file object (e.g. if the GzipFile was constructed with the
fileobj parameter).
-
mtime
When decompressing, the value of the last modification time field in
the most recently read header may be read from this attribute, as an
integer. The initial value before reading any headers is None.
All gzip compressed streams are required to contain this
timestamp field. Some programs, such as gunzip, make use
of the timestamp. The format is the same as the return value of
time.time() and the st_mtime attribute of
the object returned by os.stat().
Changed in version 3.1: Support for the with statement was added, along with the
mtime constructor argument and mtime attribute.
Changed in version 3.2: Support for zero-padded and unseekable files was added.
Changed in version 3.4: Added support for the 'x' and 'xb' modes.
Changed in version 3.5: Added support for writing arbitrary
bytes-like objects.
The read() method now accepts an argument of
None.