这里的许多答案在2015年已经过时了(尽管丹尼尔·罗斯曼最初接受的答案并没有过时)。以下是目前的情况:

Binary packages are now distributed as wheels (.whl files)—not just on PyPI, but in third-party repositories like Christoph Gohlke's Extension Packages for Windows. pip can handle wheels; easy_install cannot. Virtual environments (which come built-in with 3.4, or can be added to 2.6+/3.1+ with virtualenv) have become a very important and prominent tool (and recommended in the official docs); they include pip out of the box, but don't even work properly with easy_install. The distribute package that included easy_install is no longer maintained. Its improvements over setuptools got merged back into setuptools. Trying to install distribute will just install setuptools instead. easy_install itself is only quasi-maintained. All of the cases where pip used to be inferior to easy_install—installing from an unpacked source tree, from a DVCS repo, etc.—are long-gone; you can pip install ., pip install git+https://. pip comes with the official Python 2.7 and 3.4+ packages from python.org, and a pip bootstrap is included by default if you build from source. The various incomplete bits of documentation on installing, using, and building packages have been replaced by the Python Packaging User Guide. Python's own documentation on Installing Python Modules now defers to this user guide, and explicitly calls out pip as "the preferred installer program". Other new features have been added to pip over the years that will never be in easy_install. For example, pip makes it easy to clone your site-packages by building a requirements file and then installing it with a single command on each side. Or to convert your requirements file to a local repo to use for in-house development. And so on.

The only good reason that I know of to use easy_install in 2015 is the special case of using Apple's pre-installed Python versions with OS X 10.5-10.8. Since 10.5, Apple has included easy_install, but as of 10.10 they still don't include pip. With 10.9+, you should still just use get-pip.py, but for 10.5-10.8, this has some problems, so it's easier to sudo easy_install pip. (In general, easy_install pip is a bad idea; it's only for OS X 10.5-10.8 that you want to do this.) Also, 10.5-10.8 include readline in a way that easy_install knows how to kludge around but pip doesn't, so you also want to sudo easy_install readline if you want to upgrade that.

更新:正如一些人认为的那样，setuptools吸收了分发而不是其他方式。Setuptools是最新的，包含了最新的distutils更改和wheel格式。因此，easy_install和pip现在或多或少处于同等地位。

来源:http://pythonhosted.org/setuptools/merge-faq.html why-setuptools-and-not-distribute-or-another-name

原因有两个，可能还有更多:

PIP提供了一个卸载命令 如果安装中途失败，PIP将使您处于干净的状态。

伊恩·比金对皮普的介绍如下:

pip was originally written to improve on easy_install in the following ways All packages are downloaded before installation. Partially-completed installation doesn’t occur as a result. Care is taken to present useful output on the console. The reasons for actions are kept track of. For instance, if a package is being installed, pip keeps track of why that package was required. Error messages should be useful. The code is relatively concise and cohesive, making it easier to use programmatically. Packages don’t have to be installed as egg archives, they can be installed flat (while keeping the egg metadata). Native support for other version control systems (Git, Mercurial and Bazaar) Uninstallation of packages. Simple to define fixed sets of requirements and reliably reproduce a set of packages.

要求的文件。

说真的，我每天都将它与virtualenv结合使用。

快速依赖管理教程，伙计们

需求文件允许您创建通过pip安装的所有包的快照。通过在虚拟环境中封装这些包，你可以让你的代码库使用一组非常特定的包，并与其他人共享该代码库。

来自Heroku的文档https://devcenter.heroku.com/articles/python

您创建了一个虚拟环境，并设置shell来使用它。(bash / * nix指令)

virtualenv env
source env/bin/activate

现在所有使用该shell运行的python脚本都将使用该环境的包和配置。现在您可以在本地将包安装到此环境中，而不需要在您的机器上全局安装它。

pip install flask

现在您可以转储有关已安装的软件包的信息

pip freeze > requirements.txt

如果你将该文件签入版本控制，当其他人得到你的代码时，他们可以设置自己的虚拟环境并安装所有依赖项:

pip install -r requirements.txt

任何时候你都可以像这样自动化枯燥的工作，这真是太棒了。

pip不会安装二进制包，并且在Windows上没有经过很好的测试。

由于Windows默认没有编译器，pip通常不能在那里使用。easy_install用于安装Windows的二进制包。