4.1. Importing pyplot

Matplotlib, as many other libraries such as NumPy or Pandas, is a package that needs to be installed in addition to the standard Python packages. Normally, it should already be installed in your setup; it not, please refer to section Installing Python, Spyder and Kinetics Toolkit to install it.

Even if a package is installed, we need to tell Python to import its contents before using it. This is usually done at the beginning of the Python script, using the import statement. For the pyplot module of the Matplotlib package, we would write:

import matplotlib.pyplot

Once imported, we can access the module’s contents under the matplotlib.pyplot namespace:

matplotlib.pyplot.plot([0, 1, 4], "o-");

Note

A namespace is a name that groups different objects (functions, variables, classes). It is used to avoid ambiguities between two modules that could use identical names to define their respective objects. For instance, Python provides the function max that returns the maximum value between two floats. NumPy also provides a function max that returns the maximum value of an array. Namespaces avoid name clashes: Python’s max is accessed using max() while NumPy’s max is accessed using numpy.max().

To avoid typing matplotlib.pyplot each time we need a pyplot function, it is very common to import it using an alias:

import matplotlib.pyplot as plt

This line behaves like the previous import, but this time matplotlib.pyplot is imported into the plt namespace instead of the matplotlib.pyplot namespace. This leads to shorter and cleaner lines of code.