Python write to a gzip file

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Python gzip – compress decompress

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 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 packare not supported by this module. 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 fileobjwhich can be a regular file, a StringIO object, or any other object which simulates a file. It defaults to Nonein which case filename is opened to provide a file object. When fileobj is not Nonethe 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 fileobjif 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'. 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. 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 Nonethe current time is used. This module ignores the timestamp when decompressing; however, some programs, such as gunzipmake use of it. The format of the timestamp is the same as that of the return value of time. GzipFile supports iteration and the with statement. Changed in version 2. This is a shorthand for GzipFile filename, mode, compresslevel. The filename argument is required; mode defaults to 'rb' and compresslevel defaults to 9. The basic data compression module needed to support the gzip file format. The module defines the following items: class gzip. New in version 2. See also Module zlib The basic data compression module needed to support the gzip file format. Table of Contents

Example Uses of the Linux gzip Command


Table of Contents Previous: bz2 — bzip2 compression Next: tarfile — Tar archive access. Some of the features described here may not be available in earlier versions of Python. Now available for Python 3! Buy the book! The gzip module provides a file-like interface to GNU zip files, using zlib to compress and uncompress the data. The module-level function open creates an instance of the file-like class GzipFile. The usual methods for writing and reading data are provided. To write data into a compressed file, open the file with mode 'w'. Different amounts of compression can be used by passing a compresslevel argument. Valid values range from 1 to 9, inclusive. Lower values are faster and result in less compression. Higher values are slower and compress more, up to a point. The center column of numbers in the output of the script is the size in bytes of the files produced. As you see, for this input data, the higher compression values do not necessarily pay off in decreased storage space. Results will vary, depending on the input data. A GzipFile instance also includes a writelines method that can be used to write a sequence of strings. To read data back from previously compressed files, simply open the file with mode 'r'. The seek position is relative to the uncompressed data, so the caller does not even need to know that the data file is compressed. When working with a data stream instead of a file, use the GzipFile class directly to compress or uncompress it. This is useful when the data is being transmitted over a socket or from read an existing already open file handle. A StringIO buffer can also be used. When re-reading the previously compressed data, I pass an explicit length to read. If you are working with streams of compressed data, you may want to prefix the data with an integer representing the actual amount of data to be read. Last updated on Mar 16, Created using Sphinx. Design based on "Leaves" by SmallPark. Available In: 1. The same line, over and over. Starting at position 5 for 10 bytes: nts of the True. Note When re-reading the previously compressed data, I pass an explicit length to read. See also gzip The standard library documentation for this module.

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By default when you compress a file or folder using the gzip command it will have the same file name as it did before but with the extension. The simplest way to compress a single file using gzip is to run the following command:. Some files compress better than others. Other file types such as JPEG images and MP3 audio files do not compress at all well and the file may actually increase in size after running the gzip command against it. JPEG images and MP3 audio files are already compressed and therefore the gzip command simply adds to it rather than compressing it. Sometimes a file cannot be compressed. To force the gzip command to do its stuff simply run the following command:. By default when you compress a file using the gzip command you end up with a new file with the extension. To compress the file and keep the original file must specify the -k flag:. I you run the following command you would end up with a file called mydocument. The whole point of compressing files is about saving disk space or to reduce the size of a file prior to sending it over a network. The gzip command provides the kind of statistics you require when checking for compression performance. This process doesn't create one file called foldername. Instead, it traverses the directory structure and compresses each file in that folder structure. To compress the folder structure as one file you are better off creating a tar file and then gzipping the tar file. You can compress a file in different ways. For example, you can go for a smaller compression which will work faster or you can go for maximum compression which has the tradeoff of taking longer to run. The gzip command should not be used when working with standard zip files. You can use the zip command and unzip command for handling those files. Linux Switching from Windows. Tweet Share Email. The gzip command is a common way of compressing files within Linux. To compress a file called mydocument. The gzip command only attempts to compress regular files and folders. Use the following command to decompress a gzip archive:. To decompress the mydocument. To get the list of statistics run the following command:. The information returned by the above command is as follows:. Compressed size Uncompressed size Ratio as a percentage Uncompressed filename. Compress every file in a folder and its subfolders by using the following command:. To verify that a file is valid, run the following command:. If the file is valid there will be no output. To get minimum compression at the fastest speed run the following command:. To get maximum compression at the slowest speed run the following command:. You can vary the speed and compression level by picking different numbers between 1 and 9. More from Lifewire.

Python Support for gzip files (gzip)


GZip application is used for compression and decompression of files. It is a part of GNU project. The gzip data compression algorithm itself is based on zlib module. The gzip module contains definition of GzipFile class along with its methods. It also caontains convenience function opencompress and decompress. This function opens a gzip-compressed file in binary or text mode and returns a file like object, which may be physical file, a string or byte object. This function also defines compression level whose acceptable value is between 0 to 9. This function applies compression on the data given to it as argument and returns compressed byte object. By default compression level is 9. To compress an existing file to a gzip archive, read text in it and convert it to a bytearray. This bytearray object is then written to a gzip file. In addition to these convenience functions, gzip module also has GzipFile class which defines the compress and decompress methods. The constructor of this class takes file, mode and compressionlevel arguments exactly with same meaning as above. This will create a testnew. You can unzip it using any utility to see that it contains testnew. Arjun Thakur. Previous Page Print Page. Next Page.

Reading and Writing Files in Python

There were a lot of uninteresting results, but there were two I thought were worth sharing. Hello, can you provide some more information on the methods you used to gather those benchmark results? I ran a quick test with python 3. How big are the files that you are running this test on? I am working with pretty large files 20Gb and up and wanted to try this out to see if it makes a difference. I wrote this 3 years ago and I wonder if at the time I was still using Python 2. Certainly in Python 3 I agree with you. Perhaps this page needs to be re-run for performance. Skip to content. Instantly share code, notes, and snippets. Code Revisions 3 Stars 21 Forks 5. Embed What would you like to do? Embed Embed this gist in your website. Share Copy sharable link for this gist. Learn more about clone URLs. Download ZIP. BufferedReader gz for line in f. This comment has been minimized. Sign in to view. Copy link Quote reply. What version of Python? Content of lines I ran a quick test with python 3.

Python GZip Compress File



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