Did you import it? Importing matplotlib is not enough.
>>> import matplotlib
>>> matplotlib.pyplot
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'pyplot'
but
>>> import matplotlib.pyplot
>>> matplotlib.pyplot
works.
pyplot is a submodule of matplotlib and not immediately imported when you import matplotlib.
The most common form of importing pyplot is
import matplotlib.pyplot as plt
Thus, your statements won't be too long, e.g.
plt.plot([1,2,3,4,5])
instead of
matplotlib.pyplot.plot([1,2,3,4,5])
And: pyplot is not a function, it's a module! So don't call it, use the functions defined inside this module instead. See my example above