'Constructor for the GzipFile class.
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, a StringIO 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 includes 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\', or \'wb\',
depending on whether the file will be read or written.  The default
is the mode of fileobj if discernible; otherwise, the default is \'rb\'.
Be aware that only the \'rb\', \'ab\', and \'wb\' values should be used
for cross-platform portability.
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
at all. The default is 9.
The mtime argument is an optional numeric timestamp to be written
to the stream when compressing.  All gzip compressed streams
are required to contain a timestamp.  If omitted or None, the
current time is used.  This module ignores the timestamp when
decompressing; however, some programs, such as gunzip, make use
of it.  The format of the timestamp is the same as that of the
return value of time.time() and of the st_mtime member of the
object returned by os.stat().'

def __init__(self, filename=None, mode=None, compresslevel=9, fileobj=None, mtime=None):

    if mode:
        mode = mode.replace('U', '')
    if (mode and ('b' not in mode)):
        mode += 'b'
    if (fileobj is None):
        fileobj = self.myfileobj = __builtin__.open(filename, (mode or 'rb'))
    if (filename is None):
        if (hasattr(fileobj, 'name') and (fileobj.name != '<fdopen>')):
            filename = fileobj.name
        else:
            filename = ''
    if (mode is None):
        if hasattr(fileobj, 'mode'):
            mode = fileobj.mode
        else:
            mode = 'rb'
    if (mode[0:1] == 'r'):
        self.mode = READ
        self._new_member = True
        self.extrabuf = ''
        self.extrasize = 0
        self.extrastart = 0
        self.name = filename
        self.min_readsize = 100
    elif ((mode[0:1] == 'w') or (mode[0:1] == 'a')):
        self.mode = WRITE
        self._init_write(filename)
        self.compress = zlib.compressobj(compresslevel, zlib.DEFLATED, (- zlib.MAX_WBITS), zlib.DEF_MEM_LEVEL, 0)
    else:
        raise IOError, (('Mode    ' + mode) + '    not    supported')
    self.fileobj = fileobj
    self.offset = 0
    self.mtime = mtime
    if (self.mode == WRITE):
        self._write_gzip_header()
