pip dependency resolution fails when install both numpy and matplotlib

Question

Starting from a clean python 2.7.3 installation, if I run

pip install -r requirements.txt

with the following requirements.txt:

Flask==0.10.1
Flask-Cache==0.12
Jinja2==2.7.1
MarkupSafe==0.18
Werkzeug==0.9.4
gunicorn==18.0
itsdangerous==0.23
wsgiref==0.1.2
numpy==1.7.1
PIL==1.1.7
matplotlib==1.2.1

then pip attempts to install matplotlib before numpy and fails with:

============================================================================
BUILDING MATPLOTLIB
            matplotlib: 1.2.1
                python: 2.7.3 (default, Jan  2 2013, 13:56:14)  [GCC 4.7.2]
              platform: linux2

REQUIRED DEPENDENCIES
                 numpy: no
                        * You must install numpy 1.4 or later to build
                        * matplotlib.
Complete output from command python setup.py egg_info:
basedirlist is: ['/usr/local', '/usr']
============================================================================

However, if I do

pip install numpy
pip install -r requirements.txt

then everything works fine. What's going on here?

possible duplicate of Matplotlib requirements with pip install in virtualenv — bmu
– bmu, Commented Oct 1, 2013 at 15:52

tacaswell · Accepted Answer · 2013-10-01 14:54:47Z

2

pip doesn't naively differentiate between 'runtime' and 'compiletime' requirements. Both numpy and matplotlib have significant c/c++ extensions which need to be done in the right order.

There was a recent PR #2445 related to this which will (I think) make it into 1.3.1

answered Oct 1, 2013 at 14:54

tacaswell

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Community · Accepted Answer · 2017-05-23 12:06:37Z

1

PIP installs in alphabetical order, so in your requirements script it tries to install matplotlib before numpy. Since matplotlib is dependent on numpy it gives the error you received. Doing pip install numpy before pip install -r requirements.txt installs numpy before it goes through the requirements.txt, so this time when it gets to matplotlib, numpy is already installed.

See also: pip freeze and order of dependencies

edited May 23, 2017 at 12:06

CommunityBot

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answered Oct 1, 2013 at 14:51

Niek de Klein

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