12.2. gzip — Support for gzip files

Source code: Lib/gzip.py

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该模块提供了一个简单的界面来压缩和解压缩文件，就像GNU程序gzip和gunzip一样。

数据压缩由zlib模块提供。

gzip模块提供了在Python的文件对象之后建模的GzipFile类。GzipFile类读写gzip格式文件，自动压缩或解压缩数据，使其看起来像一个普通的文件对象。

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.

该模块定义了以下项目：

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

除了readinto()和truncate()之外，GzipFile类的构造方法可以模拟文件对象的大部分方法。方法。必须给fileobj和filename中的至少一个赋予一个非平凡的值。

新的类实例基于fileobj，它可以是常规文件，StringIO对象或任何其他模拟文件的对象。它默认为None，在这种情况下打开filename以提供文件对象。

当fileobj不是None时，filename参数仅用于包含在gzip文件头中，可能包括未压缩文件的原始文件名。如果可以识别，它默认为fileobj的文件名；否则，它默认为空字符串，在这种情况下，标头中不包括原始文件名。

mode参数可以是'r'，'rb'，'a'，'ab'，'w'或'wb'，具体取决于文件是否被读取或写入。默认是fileobj的模式，如果可以看出；否则，默认值为'rb'。如果没有给出，'b'标志将被添加到模式，以确保以二进制模式打开文件以实现跨平台的可移植性。

compresslevel参数是从0到9的整数，控制压缩级别；1最快，产生最小的压缩，而9最慢，产生最大的压缩。0没有压缩。默认值为9。

mtime参数是一个可选的数字时间戳，可在压缩时写入流中。所有gzip压缩流需要包含时间戳。如果省略或None，则使用当前时间。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.

Changed in version 2.7: Support for the with statement was added.

Changed in version 2.7: Support for zero-padded files was added.

New in version 2.7: 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. Examples of usage

Example of how to read a compressed file:

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

Example of how to create a compressed GZIP file:

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

Example of how to GZIP compress an existing file:

import gzip
f_in = open('file.txt', 'rb')
f_out = gzip.open('file.txt.gz', 'wb')
f_out.writelines(f_in)
f_out.close()
f_in.close()

See also

Module zlib

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