gzip --- gzip 檔案的支援

原始碼：Lib/gzip.py

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

The data compression is provided by the zlib module.

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.

此模組定義了以下項目：

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).

在 3.3 版的變更: Added support for filename being a file object, support for text mode, and the encoding, errors and newline arguments.

在 3.4 版的變更: 新增 'x'、'xb' 和 'xt' 模式的支援。

在 3.6 版的變更: 接受類路徑物件。

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.

在 3.8 版被加入.

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 也提供了以下的方法和屬性：

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.

備註

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).

在 3.2 版被加入.

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.

在 3.1 版的變更: Support for the with statement was added, along with the mtime constructor argument and mtime attribute.

在 3.2 版的變更: Support for zero-padded and unseekable files was added.

在 3.3 版的變更: io.BufferedIOBase.read1() 方法現在已有實作。

在 3.4 版的變更: 新增 'x' 和 'xb' 模式的支援。

在 3.5 版的變更: Added support for writing arbitrary bytes-like objects. The read() method now accepts an argument of None.

在 3.6 版的變更: 接受類路徑物件。

在 3.12 版的變更: Remove the filename attribute, use the name attribute instead.

在 3.9 版之後被棄用: 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.

在 3.2 版被加入.

在 3.8 版的變更: Added the mtime parameter for reproducible output.

在 3.11 版的變更: 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.

在 3.2 版被加入.

在 3.11 版的變更: Speed is improved by decompressing members at once in memory instead of in a streamed fashion.

用法範例

如何讀取壓縮檔案的範例：

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

如何建立一個壓縮的 GZIP 檔案的範例：

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

如何壓縮一個已存在的檔案的範例：

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)

如何壓縮一個二進位字串的範例：

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

也參考

zlib 模組

The basic data compression module needed to support the gzip file format.

命令列介面

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

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

在 3.8 版的變更: Add a new command line interface with a usage. By default, when you will execute the CLI, the default compression level is 6.

命令列選項

file

如果未指定 file，則從 sys.stdin 讀取。

--fast

Indicates the fastest compression method (less compression).

--best

Indicates the slowest compression method (best compression).

-d, --decompress

解壓縮指定的檔案。

-h, --help

顯示幫助訊息。