"gzip" --- Support for **gzip** files
*************************************

**Kod źródłowy:** Lib/gzip.py

======================================================================

This module provides a simple interface to compress and decompress
files just like the GNU programs **gzip** and **gunzip** would.

Kompresję danych zapewnia moduł "zlib".

The "gzip" module provides the "GzipFile" class, as well as the
"open()", "compress()" and "decompress()" convenience functions. The
"GzipFile" class reads and writes **gzip**-format files, automatically
compressing or decompressing the data so that it looks like an
ordinary *file object*.

Note that additional file formats which can be decompressed by the
**gzip** and **gunzip** programs, such  as those produced by
**compress** and **pack**, are not supported by this module.

Moduł definiuje następujące pozycje:

gzip.open(filename, mode='rb', compresslevel=9, encoding=None, errors=None, newline=None)

   Open a gzip-compressed file in binary or text mode, returning a
   *file object*.

   The *filename* argument can be an actual filename (a "str" or
   "bytes" object), or an existing file object to read from or write
   to.

   The *mode* argument can be any of "'r'", "'rb'", "'a'", "'ab'",
   "'w'", "'wb'", "'x'" or "'xb'" for binary mode, or "'rt'", "'at'",
   "'wt'", or "'xt'" for text mode. The default is "'rb'".

   The *compresslevel* argument is an integer from 0 to 9, as for the
   "GzipFile" constructor.

   For binary mode, this function is equivalent to the "GzipFile"
   constructor: "GzipFile(filename, mode, compresslevel)". In this
   case, the *encoding*, *errors* and *newline* arguments must not be
   provided.

   For text mode, a "GzipFile" object is created, and wrapped in an
   "io.TextIOWrapper" instance with the specified encoding, error
   handling behavior, and line ending(s).

   Zmienione w wersji 3.3: Added support for *filename* being a file
   object, support for text mode, and the *encoding*, *errors* and
   *newline* arguments.

   Zmienione w wersji 3.4: Added support for the "'x'", "'xb'" and
   "'xt'" modes.

   Zmienione w wersji 3.6: Accepts a *path-like object*.

exception gzip.BadGzipFile

   An exception raised for invalid gzip files.  It inherits from
   "OSError". "EOFError" and "zlib.error" can also be raised for
   invalid gzip files.

   Nowe w wersji 3.8.

class gzip.GzipFile(filename=None, mode=None, compresslevel=9, fileobj=None, mtime=None)

   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'".  In future Python
   releases the mode of *fileobj* will not be used.  It is better to
   always specify *mode* for writing.

   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.

      Informacja:

        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).

      Nowe w wersji 3.2.

   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()".

   name

      The path to the gzip file on disk, as a "str" or "bytes".
      Equivalent to the output of "os.fspath()" on the original input
      path, with no other normalization, resolution or expansion.

   Zmienione w wersji 3.1: Support for the "with" statement was added,
   along with the *mtime* constructor argument and "mtime" attribute.

   Zmienione w wersji 3.2: Support for zero-padded and unseekable
   files was added.

   Zmienione w wersji 3.3: The "io.BufferedIOBase.read1()" method is
   now implemented.

   Zmienione w wersji 3.4: Added support for the "'x'" and "'xb'"
   modes.

   Zmienione w wersji 3.5: Added support for writing arbitrary *bytes-
   like objects*. The "read()" method now accepts an argument of
   "None".

   Zmienione w wersji 3.6: Accepts a *path-like object*.

   Niezalecane od wersji 3.9: Opening "GzipFile" for writing without
   specifying the *mode* argument is deprecated.

gzip.compress(data, compresslevel=9, *, mtime=None)

   Compress the *data*, returning a "bytes" object containing the
   compressed data.  *compresslevel* and *mtime* have the same meaning
   as in the "GzipFile" constructor above. When *mtime* is set to "0",
   this function is equivalent to "zlib.compress()" with *wbits* set
   to "31". The zlib function is faster.

   Nowe w wersji 3.2.

   Zmienione w wersji 3.8: Added the *mtime* parameter for
   reproducible output.

   Zmienione w wersji 3.11: Speed is improved by compressing all data
   at once instead of in a streamed fashion. Calls with *mtime* set to
   "0" are delegated to "zlib.compress()" for better speed. In this
   situation the output may contain a gzip header "OS" byte value
   other than 255 "unknown" as supplied by the underlying zlib
   implementation.

gzip.decompress(data)

   Decompress the *data*, returning a "bytes" object containing the
   uncompressed data. This function is capable of decompressing multi-
   member gzip data (multiple gzip blocks concatenated together). When
   the data is certain to contain only one member the
   "zlib.decompress()" function with *wbits* set to 31 is faster.

   Nowe w wersji 3.2.

   Zmienione w wersji 3.11: Speed is improved by decompressing members
   at once in memory instead of in a streamed fashion.


Przykłady użycia
================

Przykład odczytu skompresowanego pliku:

   import gzip
   with gzip.open('/home/joe/file.txt.gz', 'rb') as f:
       file_content = f.read()

Przykład tworzenia skompresowanego pliku GZIP:

   import gzip
   content = b"Lots of content here"
   with gzip.open('/home/joe/file.txt.gz', 'wb') as f:
       f.write(content)

Przykład kompresji GZIP istniejącego pliku:

   import gzip
   import shutil
   with open('/home/joe/file.txt', 'rb') as f_in:
       with gzip.open('/home/joe/file.txt.gz', 'wb') as f_out:
           shutil.copyfileobj(f_in, f_out)

Przykład kompresji ciągu binarnego przez GZIP:

   import gzip
   s_in = b"Lots of content here"
   s_out = gzip.compress(s_in)

Zobacz także:

  Moduł "zlib"
     The basic data compression module needed to support the **gzip**
     file format.


Interfejs linii komend
======================

The "gzip" module provides a simple command line interface to compress
or decompress files.

Once executed the "gzip" module keeps the input file(s).

Zmienione w wersji 3.8: Add a new command line interface with a usage.
By default, when you will execute the CLI, the default compression
level is 6.


Opcje wiersza poleceń
---------------------

file

   If *file* is not specified, read from "sys.stdin".

--fast

   Wskazuje najszybszą metodę kompresji (mniejsza kompresja).

--best

   Wskazuje najwolniejszą metodę kompresji (najlepsza kompresja).

-d, --decompress

   Rozpakuj podany plik.

-h, --help

   Pokaż komunikat pomocy.
