changes according to community feedback + uninstall script
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Tarek Ziadé
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189
pep-0376.txt
189
pep-0376.txt
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@ -18,37 +18,41 @@ This PEP proposes various enhancements for Distutils:
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- A new format for the .egg-info structure.
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- Some APIs to read the meta-data of a project
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- An install script to install a package in Python.
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- An uninstall script to uninstall a package in Python.
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Definitions
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===========
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A **project** is a Python application composed of one or many Python packages.
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It is distributed using a `setup.py` script with Distutils and/or Setuptools.
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Once installed, one or several **packages** are added in Python's site-packages.
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Rationale
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=========
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There are three problems right now in the way packages
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are installed in Python:
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- There are too many ways to install a package in Python.
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- There is no way to uninstall a package.
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There are three problems right now in the way projects are installed in
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Python:
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- There are too many ways to install a project in Python.
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- There is no API to get the metadata of installed packages.
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How packages are installed
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How projects are installed
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--------------------------
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Right now, when a package is installed in Python, using the
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Distutils `install` command, the `install_egg_info` subcommand is
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called in order to create an `.egg-info` file in the site-packages directory,
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right beside the package itself.
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Right now, when a project is installed in Python, every package its contains
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is installed in the `site-packages` directory with the Distutils `install`
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command.
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For example, if the `zlib` package is installed, two elements
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will be installed in `site-packages`::
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The `install_egg_info` subcommand is called during this process, in order to
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create an `.egg-info` file in the `site-packages` directory.
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For example, if the `zlib` project is installed (which contains one package),
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two elements will be installed in `site-packages`::
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- zlib
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- zlib-2.5.2.egg-info
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- zlib-2.5.2-py2.4.egg-info
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Where `zlib` is the package itself, and `zlib-2.5.2.egg-info` is
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Where `zlib` is the package, and `zlib-2.5.2-py2.4.egg-info` is
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a file containing the package metadata as described in PEP 314.
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This file corresponds to the file called `PKG-INFO`, built by
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@ -59,42 +63,31 @@ to install their packages, and these third-party tools do not install
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packages in the same way that Distutils does:
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- `easy_install` creates an `EGG-INFO` directory inside an `.egg` directory,
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and adds a `PKG-INFO` file inside this directory, amongst other files.
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and adds a `PKG-INFO` file inside this directory. The `.egg` directory
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contains in that case the packages of the project.
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- `pip` creates an `.egg-info` directory inside the site-packages directory
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besides the package, and adds a `PKG-INFO` file inside it.
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and adds a `PKG-INFO` file inside it. Packages are installed in
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site-packages directory in a regular way.
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They both add other files in the `EGG-INFO` or `.egg-info` directory, and
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create or modify `.pth` files. `pip` also creates one `.pth` file
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per installed package, which may lead to slow initialisation of Python.
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create or modify `.pth` files.
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The uninstall command
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Uninstall information
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---------------------
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Python doesn't provide any `uninstall` command. If you want to uninstall
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a package, you have to be a power user and remove the package directory
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from the right site-packages directory, then look over the right pth
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files. And this method differs, depending on the tools you are using.
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Distutils doesn't provide any `uninstall` command. If you want to uninstall
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a project, you have to be a power user and remove the various package
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directories from the right `site-packages` directory, then look over the right
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`pth` files. And this method differs, depending on the tools you are using.
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The worst issue is that you depend on the way the packager created his package.
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When you call `python setup.py install`, it will not be installed the same way
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depending on the tool used by the packager (distutils or setuptools).
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depending on the tool used by the packager (mainly Distutils or Setuptools).
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But there's common behavior: files are copied in your installation.
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And there's a way to keep track of theses file, so to remove them.
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Installing a package
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--------------------
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There are too many different ways to install a package in Python:
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- by hand, by getting a distribution and running the install command
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- using `easy_install`, the script provided by setuptools
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- using `pip`
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The problem is: they do not install the package the same way,
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and Python should provide one and only one way to do it.
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What this PEP proposes
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----------------------
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@ -102,9 +95,8 @@ To address those issues, this PEP proposes a few changes:
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- a new `.egg-info` structure using a directory;
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- a list of elements this directory holds;
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- some new functions in `pkgutil`
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- addition of an install and an uninstall script
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- new functions in `pkgutil` to be able to query the information
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of installed projects.
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.egg-info becomes a directory
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=============================
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@ -124,48 +116,57 @@ For example, if the `zlib` package is installed, two elements
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will be installed in `site-packages`::
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- zlib
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- zlib-2.5.2-py2.6.egg-info/
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- zlib-2.5.2.egg-info/
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PKG-INFO
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To be able to implement this change, the impacted code in Distutils
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is the `install_egg_info` command.
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The Python version will also be removed from the .egg-info directory
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name. To be able to implement this change, the impacted code in Distutils
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is the `install_egg_info` command, and the various third-party projects.
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Adding a RECORD in the .egg-info directory
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==========================================
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Adding MANIFEST and RECORD in the .egg-info directory
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=====================================================
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Some files can be added inside the `.egg-info` directory at installation
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time. They will all be UPPERCASE files.
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- the `MANIFEST` file built by the `sdist` command. Notice that
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some fixes were made lately on the default file names added in `MANIFEST`
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when `MANIFEST.in` is not provided (see #2279 for instance).
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A `RECORD` file will be added inside the `.egg-info` directory at installation
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time.
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- the `RECORD` file will hold the list of installed files. These
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correspond to the files listed by the `record` option of the `install`
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command, and will always be generated. This will allow uninstall, as
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explained later in this PEP.
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The two files will need to use '/'-separated relative paths.
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The `install` command will record by default installed files in the
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RECORD file.
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RECORD file, using these rules:
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The `sdist` module will introduce an `EGG_INFO_FILES` constant to list
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all files located in the `.egg-info` directory::
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- if the installed file is located in a directory in `site-packages`,
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it will be a '/'-separated relative path, no matter what is the target
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system. This makes this information cross-compatible and allows simple
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installation to be relocatable.
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- if the installed file is located elswhere in the system, a
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'/'-separated absolute path is used.
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This will require changing the way the `install` command writes the record
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file, so the old `record` behavior will be deprecated.
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XXX see how to handle old record (new option, or wait for 2 version?)
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Listing the .egg-info elements in Distutils
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===========================================
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In Distutils, the `dist` module will introduce an `EGG_INFO_FILES` constant
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to list all files located in the `.egg-info` directory::
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from collections import namedtuple
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EggInfos = namedtuple('EggInfo', 'manifest record pkg_info')
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# files added in egg-info
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EGG_INFO_FILES = EggInfos('MANIFEST', 'RECORD', 'PKG-INFO')
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EGG_INFO_FILES = EggInfos('RECORD', 'PKG-INFO')
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Back to our `zlib` example, we will have::
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- zlib
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- zlib-2.5.2.egg-info/
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PKG-INFO
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MANIFEST
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RECORD
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XXX See if we want to add Python version in the PKG-INFO
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@ -176,7 +177,6 @@ New functions in pkgutil
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To use the `.egg-info` directory content, we need to add in the standard
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library a set of APIs. The best place to put these APIs seems to be `pkgutil`.
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The new functions added in the package are :
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- get_egg_info(project_name) -> path or None
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@ -216,57 +216,38 @@ Let's use it with our `zlib` example::
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files
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Adding an install and an uninstall script
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=========================================
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Adding an Uninstall API
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=======================
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XXX decide wheter we include these scripts.
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Distutils provides a very basic way to install a project, which is running
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the `install` command over the `setup.py` script of the distribution.
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`easy_install` and `pip` does basically the same work, besides other features
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that are not discussed here.
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Distutils will provide a very basic `uninstall` command that will remove
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all files listed in the `RECORD` file of a project, as long as they are not
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mentioned in another `RECORD` file.
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- they look for the package at PyPI
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- they download it and build it
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- they install it inside the site-packages directory
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- they add an entry in a .pth file
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This command will be added in the `util` module and will take the name
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of the project to uninstall::
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Distutils will provide two simple reference scripts, that are just able
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to do the features mentioned. Third party packages will be able to fetch
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dependencies.
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>>> from distutils.util import uninstall
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>>> uninstall('zlib')
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Install script
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--------------
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To make it a reference API for third-party projects that wish to provide
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an `uninstall feature`. The `uninstall` API can also be invoked with a
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second callable argument, that will be invoked for each file to be removed.
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If it returns `True`, the file will be removed.
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A new script called `install.py` is added in a new directory called `scripts`
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in Distutils, and lets people run an installation using::
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Examples::
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$ python -m distutils.scripts.install zlib
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>>> def _remove_and_log(path):
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... logging.info('Removing %s' % path)
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... return True
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>>> uninstall('zlib', _remove_and_log)
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>>> def _dry_run(path):
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... logging.info('Removing %s (dry run)' % path)
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... return False
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>>> uninstall('zlib', _dry_run)
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Where `zlib` can be:
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- the name of the package
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- an url of an archive
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- a path
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The install script process is done in 3 steps:
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1. it looks for the package at PyPI if it's a package name
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XXX explain here how (easy_install code)
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2. it downloads it in a temporary directory (or copy it if it's a path)
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3. it runs the install command, with the --record option
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XXX explains here how (see pip code)
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The install script takes several options :
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Uninstall script
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----------------
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An uninstall command is added as well that removes the files recorded
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in the RECORD file. This removal will warn on files that no longer exist
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and will not take care of side effects, like the removal of a file
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used by another element of the system.
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$ python -m distutils.scripts.uninstall zlib
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XXX work to be done here : detail specification of the uninstall process
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Aknowledgments
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==============
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