python的pip 安装

python的pip 安装

python有很多好用的包，但是需要的时候一一安装实在是麻烦，还好有pip这么好用的安装工具。所以第一步是安装pip，然后其它软件都so easy！

文章来源：https://packaging.python.org/installing/#id11

Requirements for Installing Packages

This section describes the steps to follow before installing other Python packages.

Install pip, setuptools, and wheel

• If you have Python 2 >=2.7.9 or Python 3 >=3.4 installed from python.org, you will already havepip and setuptools, but will need to upgrade to the latest version:

  On Linux or OS X:

  pip install -U pip setuptools
  

  On Windows:

  python -m pip install -U pip setuptools
  

• If you’re using a Python install on Linux that’s managed by the system package manager (e.g “yum”, “apt-get” etc...), and you want to use the system package manager to install or upgrade pip, then see Installing pip/setuptools/wheel with Linux Package Managers

• Otherwise:

• Securely Download get-pip.py [1]

• Run python get-pip.py. [2] This will install or upgrade pip. Additionally, it will install setuptoolsand wheel if they’re not installed already.

  Warning

  Be cautious if you’re using a Python install that’s managed by your operating system or another package manager. get-pip.py does not coordinate with those tools, and may leave your system in an inconsistent state. You can use python get-pip.py --prefix=/usr/local/ to install in /usr/local which is designed for locally-installed software.

Optionally, Create a virtual environment

See section below for details, but here’s the basic commands:

Using virtualenv:

pip install virtualenv
virtualenv <DIR>
source <DIR>/bin/activate

Using venv: [3]

python3 -m venv <DIR>
source <DIR>/bin/activate

Creating Virtual Environments

Python “Virtual Environments” allow Python packages to be installed in an isolated location for a particular application, rather than being installed globally.

Imagine you have an application that needs version 1 of LibFoo, but another application requires version 2. How can you use both these applications? If you install everything into /usr/lib/python2.7/site-packages (or whatever your platform’s standard location is), it’s easy to end up in a situation where you unintentionally upgrade an application that shouldn’t be upgraded.

Or more generally, what if you want to install an application and leave it be? If an application works, any change in its libraries or the versions of those libraries can break the application.

Also, what if you can’t install packages into the global site-packages directory? For instance, on a shared host.

In all these cases, virtual environments can help you. They have their own installation directories and they don’t share libraries with other virtual environments.

Currently, there are two viable tools for creating Python virtual environments:

• venv is available by default in Python 3.3 and later, and installs pip and setuptools into created virtual environments in Python 3.4 and later.
• virtualenv needs to be installed separately, but supports Python 2.6+ and Python 3.3+, and pip,setuptools and wheel are always installed into created virtual environments by default (regardless of Python version).

The basic usage is like so:

Using virtualenv:

virtualenv <DIR>
source <DIR>/bin/activate

Using venv:

python3 -m venv <DIR>
source <DIR>/bin/activate

For more information, see the virtualenv docs or the venv docs.

Use pip for Installing

pip is the recommended installer. Below, we’ll cover the most common usage scenarios. For more detail, see the pip docs, which includes a complete Reference Guide.

There are a few cases where you might want to use easy_install instead of pip. For details, see the thepip vs easy_install breakdown in the Advanced Topics section.

Installing from PyPI

The most common usage of pip is to install from the Python Package Index using a requirement specifier. Generally speaking, a requirement specifier is composed of a project name followed by an optional version specifier. PEP 440 contains a full specification of the currently supported specifiers. Below are some examples.

To install the latest version of “SomeProject”:

pip install 'SomeProject'

To install a specific version:

pip install 'SomeProject==1.4'

To install greater than or equal to one version and less than another:

pip install 'SomeProject>=1,<2'

To install a version that’s “compatible” with a certain version: [4]

pip install 'SomeProject~=1.4.2'

In this case, this means to install any version “==1.4.*” version that’s also “>=1.4.2”.

Upgrading packages

Upgrade an already installed SomeProject to the latest from PyPI.

pip install --upgrade SomeProject