Python，matplotlib使用ipython而不是使用python加载

Question

When I try to load matplotlib using python I get an error about loading the backports.functools_lru_cache module. When I try to load matplotlib using ipython it loads just fine.

As near as I can tell ipython uses the same version of python that calling python uses. I've gone through the path that both python and ipython use and uninstalled matplotlib and backports.functools_lru_cache. I've tried then reinstalling using apt and pip, always uninstalling the previous attempt before trying the next.

I've gone through a bunch of stackexchange solutions and tried some github solutions without any luck. I run Ubuntu 18.04.

Error:

Python 2.7.15rc1 (default, Apr 15 2018, 21:51:34) 
[GCC 7.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import matplotlib
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/dist-packages/matplotlib/__init__.py", line 127, in <module>
    from matplotlib.rcsetup import defaultParams, validate_backend, cycler
  File "/usr/lib/python2.7/dist-packages/matplotlib/rcsetup.py", line 29, in <module>
    from matplotlib.fontconfig_pattern import parse_fontconfig_pattern
  File "/usr/lib/python2.7/dist-packages/matplotlib/fontconfig_pattern.py", line 32, in <module>
    from backports.functools_lru_cache import lru_cache
ImportError: No module named functools_lru_cache

I won't show ipython, because it loads just fine.

Update:

If I install using:

pip install matplotlib==2.0.2

matplotlib works for both python and ipython.

Answer 1

The problem appears to be a path problem I am not sure how to solve. I use apt on Ubuntu 18.04 to install system modules into /usr/lib/python2.7/dist-packages/. This directory is where backports.functools_lru_cache lives. I also have some compiled modules installed in /usr/local/lib/python2.7/dist-packages/ where there is a backports module WITHOUT functools_lru_cache. The problem is that python is not following the system path and only seems to be looking in /usr/local/lib/python2.7/dist-packages/ for backports. However, ipython looks in both which is why ipython was working while python was not.

python:

Python 2.7.15rc1 (default, Apr 15 2018, 21:51:34) 
[GCC 7.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.path
['', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-x86_64-linux-gnu', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/home/brendan/.local/lib/python2.7/site-packages', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/gtk-2.0']
>>> import backports
>>> backports.__path__
['/usr/local/lib/python2.7/dist-packages/backports']

ipython:

Python 2.7.15rc1 (default, Apr 15 2018, 21:51:34) 
Type "copyright", "credits" or "license" for more information.

IPython 5.5.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: sys.path
Out[1]: 
['',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-x86_64-linux-gnu',
 '/usr/lib/python2.7/lib-tk',
 '/usr/lib/python2.7/lib-old',
 '/usr/lib/python2.7/lib-dynload',
 '/home/brendan/.local/lib/python2.7/site-packages',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/gtk-2.0']

In [2]: import backports

In [3]: backports.__path__
Out[3]: 
['/usr/local/lib/python2.7/dist-packages/backports',
 '/usr/lib/python2.7/dist-packages/backports']

Solution:

To solve the problem I manually copied functools_lru_cache.py from /usr/lib/python2.7/dist-packages/backports/ to /usr/local/lib/python2.7/dist-packages/backports/. Now I can run matplotlib 2.2.2 no problem in python and ipython.

I'm going to mark this answered because my question now revolves around python and path.