Time for action – importing modules

Importing modules can be done in the following manner:

1. If the filename is, for instance, mymodule.py, import it as follows:

   >>> import mymodule
   

2. The standard Python distribution has a math module. After importing it, list the functions and attributes in the module as follows:

   >>> import math
   >>> dir(math)
   ['__doc__', '__file__', '__name__', '__package__', 'acos', 'acosh', 'asin', 'asinh', 'atan', 'atan2', 'atanh', 'ceil', 'copysign', 'cos', 'cosh', 'degrees', 'e', 'erf', 'erfc', 'exp', 'expm1', 'fabs', 'factorial', 'floor', 'fmod', 'frexp', 'fsum', 'gamma', 'hypot', 'isinf', 'isnan', 'ldexp', 'lgamma', 'log', 'log10', 'log1p', 'modf', 'pi', 'pow', 'radians', 'sin', 'sinh', 'sqrt', 'tan', 'tanh', 'trunc']
   

3. Call the pow() function in the math module:

   >>> math.pow(2, 3)
   8.0
   

   Notice the dot in the syntax. We can also import a function directly and call it by its short name. Import and call the pow() function as follows:

   >>> from math import pow
   >>> pow(2, 3)
   8.0
   

4. Python lets us define aliases for imported modules and functions. This is a good time to introduce the import conventions we are going to use for NumPy and a plotting library we will use a lot:

   import numpy as np
   import matplotlib.pyplot as plt

What just happened?

We learned about modules, importing modules, importing functions, calling functions in modules, and the import conventions of this book. This concludes the Python refresher.