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Which is the recommended way to plot: matplotlib or pylab?

Posted by: admin November 30, 2017 Leave a comment

Questions:

I see that I can plot in Python using either:

import matplotlib
matplotlib.pyplot.plot(...)

Or:

import pylab
pylab.plot(...)

Both of these use the same matplotlib plotting code.

So, which of these does the Python community recommend as the better method to plot? Why?

Answers:

Official docs: http://matplotlib.org/faq/usage_faq.html#matplotlib-pylab-and-pyplot-how-are-they-related

Both of those imports boil down do doing exactly the same thing and will run the exact same code, it is just different ways of importing the modules.

Also note that matplotlib has two interface layers, a state-machine layer managed by pyplot and the OO interface pyplot is built on top of, see How can I attach a pyplot function to a figure instance?

pylab is a clean way to bulk import a whole slew of helpful functions (the pyplot state machine function, most of numpy) into a single name space. The main reason this exists (to my understanding) is to work with ipython to make a very nice interactive shell which more-or-less replicates MATLAB (to make the transition easier and because it is good for playing around). See pylab.py and matplotlib/pylab.py

At some level, this is purely a matter of taste and depends a bit on what you are doing.

If you are not embedding in a gui (either using a non-interactive backend for bulk scripts or using one of the provided interactive backends) the typical thing to do is

import matplotlib.pyplot as plt
import numpy as np

plt.plot(....)

which doesn’t pollute the name space. I prefer this so I can keep track of where stuff came from.

If you use

ipython --pylab

this is equivalent to running

from pylab import * 

It is now recommended that for new versions of ipython you use

ipython --matplotlib

which will set up all the proper background details to make the interactive backends to work nicely, but will not bulk import anything. You will need to explicitly import the modules want.

import numpy as np
import matplotlib.pyplot as plt

is a good start.

If you are embedding matplotlib in a gui you don’t want to import pyplot as that will start extra gui main loops, and exactly what you should import depends on exactly what you are doing.