Creating Functions - Lesson 7


  • How can I define new functions?
  • What’s the difference between defining and calling a function?
  • What happens when I call a function?


  • Define a function that takes parameters.
  • Return a value from a function.
  • Set default values for function parameters.
  • Document our functions.
  • Explain why we should divide programs into small, single-purpose functions.


Jupyter Notebook File

Please use the Jupyter notebook named "07CreatingFunctions.ipynb" for this lesson. If you haven't downloaded them already, you may find them here.

Key Points

  • Define a function using def function_name(parameter).
  • The body of a function must be indented.
  • Call a function using function_name(value).
  • Numbers are stored as integers or floating-point numbers.
  • Variables defined within a function can only be seen and used within the body of the function.
  • If a variable is not defined within the function it is used, Python looks for a definition before the function call
  • Use help(thing) to view help for something.
  • Put docstrings in functions to provide help for that function.
  • Specify default values for parameters when defining a function using name=value in the parameter list.
  • Parameters can be passed by matching based on name, by position, or by omitting them (in which case the default value is used).