Functions in Programming Quiz

Introduction to Functions

• Function: group of statements performing a specific task
• Functions are for modularizing large programs
• Divided into smaller, manageable tasks
• Using functions improves organization, code reuse, and debugging
• The divide-and-conquer approach using functions

Void Functions and Value-Returning Functions

• Void function: executes statements and terminates.
• Value-returning function: executes statements, returns a value. Examples include input(), int(), float().

Defining and Calling a Void Function

• Functions are named following specific naming rules:
  • Cannot use keywords as a function name.
  • Cannot contain spaces.
  • The first character must be a letter or underscore.
  • All other characters must be a letter, number, or underscore.
  • Uppercase and lowercase characters are distinct.
• Function name should be descriptive of its task. Examples include calculate_gross_pay().
• Function definition: specifies what the function does.
• Function header: first line of a function def function_name():.
• Block: set of statements that belong together (within a function).
• Executing a function: Function definitions don't execute—you need to call them.
• When a function is called: Interpreter jumps to the function, executes the block of statements, and resumes execution at the point that called the function (known as function return).

Example of Defining and Calling a Function

• message() function defines a function containing print statements.
• The code includes a call to message() to execute the function.

Defining and Calling a Void Function (cont.)

• Main Function:
  • Called when a program starts.
  • Calls other functions when needed.
  • The main logic of the program.

Benefits of Modularizing a Program with Functions

• Simplifies code.
• Enables code reuse.
• Improves testing and debugging.
• Increases the speed of development.
• Facilitates teamwork. Different developers can work on different functions.

Indentation in Python

• Indentation is fundamental in Python for grouping statements.
• Proper indentation structures the Python code.
• Use spaces or tabs for indentation, not both, as this can be confusing.

Designing a Program to Use Functions

• Flowchart representation: function calls are shown as rectangles with vertical bars.
• Top-down design technique for breaking down algorithms into functions.
• Hierarchy chart is used to depict relationship between functions and functions called by other functions.

Local Variables

• Local variable: a variable assigned a value inside a function.
• Belongs to the function that created it.
• Accessible only inside that function.

Passing Arguments to Functions

• Argument: the data passed to a function when called.
• Parameter: a variable that receives an argument.
• Arguments are passed by position. The first argument is assigned to the first parameter, and so on.
• Scope of a parameter: the function in which the parameter is used.

Passing Multiple Arguments

• Python allows defining functions to use multiple arguments.
• Multiple arguments are passed to the function within the parentheses separated by commas. The order of the arguments matters; they're assigned to the parameters according to the position and order that they are provided.

Keyword Arguments

• Keyword arguments allow specifying which parameter the argument is assigned to.
• Order within the function call is irrelevant as long as the required parameter value is included.

Global Variables

• Global variables: Created by assignment statements outside all functions.
• Accessible from any statement in the program.
• To change a global variable, you must use global keyword within a function.

Global Constants

• Global constants: global names referring to unchanging values.
• Use global keyword to simulate constants in Python.

Introduction to Value-Returning Functions: Generating Random Numbers

• Value-returning functions return a value to the part of the program that called it.
• random module: contains functions that generate random numbers.

Standard Library Functions and the import Statement

• Standard library: collection of pre-written functions; print(), input(), range().
• Functions are often treated as "black boxes."
• import statement makes a library available for use.

Writing Your Own Value-Returning Functions

• Define a function.
• Give it parameters.
• Use a return statement.
• The function returns a value. You can assign the return value to a variable or use it in an expression.

Using IPO Charts

• IPO chart: Tool for describing function inputs, processing, and outputs.
• Columns are typically used to display the Input, Process, and Output.

Returning Strings

• Functions can return string values, containing text, characters, or words.

Returning Boolean Values

• Boolean functions return either True or False.
• Boolean values are used in decision and repetition structures.
• They simplify input validation, performing even checks, and more.

Returning Multiple Values

• Functions can return multiple values separated by a comma.
• Multiple variables are needed on the left side of the = operator to capture the returned values.

Returning None From a Function

• None signifies the absence of a value.
• Returning None is used to indicate errors in functions.

The math Module

• Provides mathematical functions.
• Imports math module (e.g., import math).
• math module libraries provide functions (math.sqrt(), math.pi, math.e).

Storing Functions in Modules

• Modules organize groups of related functions.
• Modules are important in organized, larger Python projects.
• Python code stored within a file with a .py extension can be accessed via an import statement.
• Modules can be accessed with module.function() syntax.

Menu Driven Programs

• Menu Driven programs present a list of operations to the user.
• A menu is used for displaying the list of operations.
• Uses decision structures to determine the option from the menu. Repetitive until user selects quit.

Conditionally Executing the main Function

• Main function execution is restricted by including code within if __name__=='__main__':.
• Python’s built-in __name__ variable is set to __main__ when the file is run directly.

Turtle Graphics

• Turtle graphics package for drawing shapes on the screen.
• Functions help in modularizing the drawing of standard shapes (squares, circles, lines, etc.) within a program.