6.5 Return values

Functions in Python are powerful tools that let you organize and reuse code. They can take input, process it, and give back results using return statements. This makes your code more efficient and easier to understand.

Return values are the output of functions, which you can use in other parts of your code. By using multiple return statements, you can handle different scenarios within a single function, making your code more flexible and responsive to various conditions.

Functions and Return Values

Function of return statements

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• Immediately terminates function execution and returns control back to calling code
  • Code after

    return

    statement within function will not be executed
• Can optionally be followed by expression or value, which becomes function's return value
  • If no expression provided or

    return

    omitted, function returns

    [None](https://www.fiveableKeyTerm:None)

    by default (void function)
• Returned value can be captured by calling code and used for further processing or assignment
• Multiple

  return

  statements can be used within function to provide different return values based on certain conditions
  • Allows for early termination of function based on specific scenarios (error handling, input validation)

Usage of return values

• Value returned by function can be directly used in expressions or assignments

  [def](https://www.fiveableKeyTerm:def) square(x):
      return x ** 2
  
  result = square(5) + 10
  print(result)  # Output: 35
  

  • Return value of

    square(5)

    is

    25

    , which is then added to

    10

    in expression
• Return values can be assigned to variables for later use

  def get_name():
      return "John"
  
  name = get_name()
  print("Hello, " + name)  # Output: Hello, John
  

  • Return value of

    get_name()

    is assigned to variable

    name

    for further usage (printing, concatenation)

Multiple returns in functions

• Functions can have multiple

  return

  statements to handle different scenarios or conditions

  def is_even(num):
      if num % 2 == 0:
          return True
      else:
          return False
  

  • If

    num

    is divisible by 2 (even), function returns

    True

  • Otherwise, it returns

    False

    (odd numbers)
• Multiple

  return

  statements can provide different return values based on specific conditions

  def get_grade(score):
      if score >= 90:
          return "A"
      elif score >= 80:
          return "B"
      elif score >= 70:
          return "C"
      else:
          return "F"
  

  1. Function returns different grade letters based on provided

     score

     value (argument)
  2. First

     return

     statement that satisfies condition is executed
  3. Function terminates immediately after executing matching

     return

     statement
• Useful for implementing complex logic or branching paths within function (data validation, error handling, game logic)

Function Design and Effects

• Parameters are variables defined in the function's declaration that accept input values
• Functions can have side effects, which are changes made to the program's state outside the function's local scope
• Pure functions always produce the same output for the same input and have no side effects