没有VirtualEnv的Python2.7中的站点包

Question

When I use pip install matplotlib --upgrade it runs and installs matplotlib and all dependicies, and at the end reads uninstalled version '1.3.1' . Running python and matplotlib.__version__ outputs '1.3.1' again, even though it was just declared uninstalled. How do I switch which python I'm running from, which would hopefully be where pip is installing and updating packages?

Edit: Running Mac OS 10.10.1, using python from bash.

which pip returns /usr/local/bin/pip and which -a python returns

/opt/local/bin/python
/opt/local/bin/python
/Library/Frameworks/Python.framework/Versions/Current/bin/python
/Library/Frameworks/Python.framework/Versions/Current/bin/python
/Library/Frameworks/Python.framework/Versions/Current/bin/python
/Library/Frameworks/Python.framework/Versions/2.6/bin/python
/usr/bin/python

which I'm assuming is the problem. I've deleted 2.6 before, but my Mac uses it and I had to restore my OS. How do I switch amongst them.

Answer 1

Your problem appears to be that you have two or more Python 2.7 installations, and the first python on the PATH comes from one installation (the MacPorts version, at /opt/local/bin/python ), while the first pip on the PATH comes from a different one (you haven't said which, but I'd guess it's /usr/local/bin/pip , and it's attached to either the pre-installed Apple Python or yet another Python).

If you want to have lots of Pythons installed all over the filesystem and switch among them without using virtualenv , you just need to write some scripts with modify your PATH . (And your PYTHONPATH , if you use one… but hopefully you don't.)

But I wouldn't recommend that. If you want to use the MacPorts Python:

• Make sure you have the MacPorts pip installed (it should be in /opt/local/bin/pip ). I don't know if MacPorts has a separate python-pip package, or expects you to install it manually , or otherwise.
• If you don't know how to rehash your shell cache, just open a new Terminal window after getting the MacPorts pip installed. Or, to be safe, just explicitly use /opt/local/bin/pip until the next time you logout and back in.
• When you write scripts, you may want to #!/opt/local/bin/python instead of #!/usr/bin/env python .
• Uninstall every other Python except the MacPorts one and the pre-installed Apple ones.
• Any packages you accidentally installed for other Python installations, just reinstall them for MacPorts. Also, you should usually check for ports first, like port install python-ipython or port install python27-ipython , and only fall back to pip if there is no portfile.

As a side note, many people who have this problem also have MacPorts colliding with Homebrew (or sometimes Fink, gentoo-alt, or other package managers, but none of them are very common nowadays). If you're using two such package managers, you really, really shouldn't be unless you know what you're doing. I'd disable one entirely (at least take it off your PATH, if not uninstall it). You will likely have to rebuild a bunch of stuff after you do so, but it's better than having a bunch of stuff that kind of sometimes works…