There are three pylabs that one may encounter in using Python. Two have been around for a while, and the third just showed up less than a month ago.
The “real” pylab is the procedural interface to matplotlib, i.e. a MATLAB-like command line interface. It imports matplotlib.pyplot and numpy into a single namespace. You can use it from ipython’s prompt by calling the magic function “%pylab”. It is no longer recommended by the matplotlib people. The recommended way is to import with abbreviated namespace names, and use the qualified functions. For example:
import matplotlib.pyplot as pltimport numpy as npThen there is the idea/proposal by Keir Mierle to improve on the pylab idea of a single package one might use to utilize Python for interactive analysis. This is written up in the SciPy wiki, but does not seem to have been updated since 2012.
x = np.linspace(0, 2, 100)
plt.plot(x, x, label='linear')plt.plot(x, x**2, label='quadratic')plt.plot(x, x**3, label='cubic')
plt.xlabel('x label')plt.ylabel('y label')
And finally, if you are like me, and have not been thinking too hard, and typed “pip install pylab” you get this new package from PyPI, first added on 2015-04-23. It does nothing but pull in several other Python packages, i.e. it serves as a metapackage. You can see the source is basically a dummy, with all the action in the requirements defined in setup.py.