10 Functions in `Python`

We’ve learned how to use built-in functions to analyze data, but sometimes it’s more helpful to (A) do the math by hand or (B) write your own function. Let’s learn how!

Getting Started

Packages

We’ll use base Python here. No extra packages needed.

10.1 Coding your own function!

Functions are machines that do a specific calculation using an input to produce a specific output.

Below, we’ll write an example function, called add(a, b).

This function takes two numeric values, a and b, as inputs, and adds them together.
Using def, we’ll tell Python that our function contains two inputs, a and b.
The function can involve multiple operations inside it. But at the end, you need to print one final output, or put return before your output.

# Make function
def add(a, b):
  # Compute and directly output
  return a + b

add(1, 2)

## 3

# This also works
def add(a, b):
  # Assign output to a temporary object
  output = a + b
  # Return the temporary object 'output'
  return output

add(1, 2)

## 3

10.2 Functions with Default Inputs

You can assign default input values. Below, by default, b = 2. If we supply a different b, the default gets overwritten.

def add(a, b = 2):
  return a + b

Let’s try it!

# Only provide 'a'
add(1)

## 3

# Provide both
add(1, 2)

## 3

# Change 'b'
add(1, 3)

## 4

# clear data
del add

Conclusion

Great! Let’s go make some functions!

10 Functions in Python