12.2. gzip — 对 gzip 格式的支持

源代码： Lib/gzip.py

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此模块提供的简单接口帮助用户压缩和解压缩文件，功能类似于 GNU 应用程序 gzip 和 gunzip。

数据压缩由 zlib 模块提供。

The gzip module provides the GzipFile class which is modeled after Python’s File Object. The GzipFile class reads and writes gzip-format files, automatically compressing or decompressing the data so that it looks like an ordinary file object.

注意，此模块不支持部分可以被 gzip 和 gunzip 解压的格式，如利用 compress 或 pack 压缩所得的文件。

这个模块定义了以下内容：

class gzip.GzipFile([filename[, mode[, compresslevel[, fileobj[, mtime]]]]])

Constructor for the GzipFile class, which simulates most of the methods of a file object, with the exception of the readinto() and truncate() methods. 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 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', 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'. If not given, the ‘b’ flag will be added to the mode to ensure the file is opened in binary mode 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. 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 attribute of the object returned by os.stat().

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 a StringIO object opened for writing as fileobj, and retrieve the resulting memory buffer using the StringIO object’s getvalue() method.

GzipFile supports iteration and the with statement.

在 2.7 版更改: Support for the with statement was added.

在 2.7 版更改: Support for zero-padded files was added.

2.7 新版功能: The mtime argument.

gzip.open(filename[, mode[, compresslevel]])

This is a shorthand for GzipFile(filename, mode, compresslevel). The filename argument is required; mode defaults to 'rb' and compresslevel defaults to 9.

12.2.1. 用法示例

如何读取一个压缩文件：

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

如何创建一个 GZIP 文件：

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

如何使用 GZIP 压缩一个已有的文件：

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

参见

模块 zlib

支持 gzip 格式所需要的基本压缩模块。