Glossary

6.5 Return values

2 min read•june 24, 2024

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

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 , 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 ()
  • 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 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 ()
    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
  • Pure functions always produce the same output for the same input and have no side effects

Key Terms to Review (24)

Argument: An argument is a value that is passed to a function when it is called. Arguments are used by functions to perform operations or calculations based on the provided input.
Argument: An argument is a set of statements, known as premises, that provide support for a conclusion. It is a fundamental concept in programming, particularly in the context of functions and their ability to accept and process input data.
Built-in function: A built-in function is a function provided by Python that is always available and does not require any additional imports. Examples include functions like len(), max(), min(), and abs().
Def: The 'def' keyword in Python is used to define a function, which is a reusable block of code that performs a specific task. Functions allow programmers to break down complex problems into smaller, more manageable parts, making the code more organized, efficient, and easier to maintain.
Early Termination: Early termination refers to the premature ending of a function or process before it has completed its intended execution. This concept is particularly relevant in the context of return values, where a function may exit prematurely without reaching the end of its code block.
Float: A float is a data type in programming that represents a decimal number, allowing for the storage of numbers with a fractional component. Floats are used to handle numerical values that require precision beyond what can be represented by integers.
Function: A function is a reusable block of code that performs a specific task or operation. It is a fundamental concept in programming that allows for the modularization and organization of code, promoting efficiency, readability, and maintainability.
Function Output: Function output refers to the value or data that a function returns after it has been executed. It is the result of the computations or operations performed within the function, which can then be used or manipulated in the program.
Functional Programming: Functional programming is a programming paradigm that emphasizes the use of pure functions, where the output of a function depends solely on its input, without modifying any external state. This approach promotes code that is more declarative, modular, and easier to reason about, making it a powerful tool for solving complex problems in a wide range of applications, including in the context of Python programming.
Instance method: An instance method is a function defined inside a class that operates on instances of that class. It can access and modify the data attributes of the instance.
Int: The 'int' data type in Python represents whole numbers or integers, which are numbers without fractional parts. It is a fundamental data type that is used extensively in programming to store and manipulate numeric values.
Len(): The len() function is a built-in function in Python that returns the length or count of elements in a given object, such as a string, list, tuple, or dictionary. It is a fundamental operation that is widely used across various programming topics in Python.
List: A list in Python is an ordered collection of items, where each item can be of a different data type. Lists are one of the most fundamental and versatile data structures in the Python programming language, allowing you to store and manipulate multiple values in a single variable.
Method: A method is a function that is defined within a class or an object. It encapsulates a specific behavior or action that an object can perform, allowing it to interact with its data and other objects.
None: None is a special constant in Python that represents the absence of a value or a null value. It is often used as a return value for functions that do not explicitly return a value, indicating that the function has completed but there is no data to return. This concept connects closely with return values in Python, where None is often seen as the default output when no return statement is provided.
Pure Function: A pure function is a function that, given the same input, will always return the same output and has no side effects. It relies solely on the arguments passed to it and does not depend on or modify any external state.
Return: The term 'return' in programming refers to the action of a function or method sending a value back to the code that called it. It is a fundamental concept that allows functions to communicate with the rest of a program, providing useful output or results based on the input they receive.
Return statement: A return statement is used in a function to send a result back to the caller. It terminates the execution of the function and can optionally pass back an expression or value.
Return Statement: The return statement in programming is used to exit a function and optionally return a value back to the caller. It is a crucial component that allows functions to communicate with the rest of the code by providing output or results.
Return Values: Return values refer to the output or result that a function or method in a programming language sends back to the code that called it. They allow functions to communicate information and pass data back to the rest of the program.
Scope: Scope refers to the visibility and accessibility of variables, functions, and other programming elements within different parts of a code. It determines where these elements can be accessed and used throughout the program.
Side effect: A side effect is an outcome of a function that occurs beyond its intended purpose, often altering the state of the program or affecting variables outside the function's scope. This phenomenon highlights the behavior of functions in programming, particularly when discussing how functions can interact with external data or the environment, thus creating unintended changes in state.
String: A string is a sequence of characters, such as letters, numbers, and symbols, that is used to represent and store textual data in programming. Strings are a fundamental data type in many programming languages, including Python, and are essential for tasks such as text manipulation, data storage, and communication.
Void Function: A void function, also known as a procedure or subroutine, is a type of function in programming that does not return a value. Instead, it performs a specific task or set of tasks without producing an output that can be stored or used elsewhere in the code.
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