Python Functions and Selection Statements

Introduction

This study guide covers the definition and use of functions in Python, with a focus on selection statements and test case development. These concepts are foundational for computational problem-solving and are often used to model mathematical processes in Precalculus and other STEM courses.

Expressions: Relational Operators

Relational operators are used to compare values and produce Boolean results (True or False). They are essential in selection statements for decision-making in code.

• ==: Equal to

• !=: Not equal to

• <: Less than

• >: Greater than

• <=: Less than or equal to

• >=: Greater than or equal to

Example: returns True if x is greater than 5.

Statements: Selection Statements and Return Statement

Selection statements allow a program to choose different paths of execution based on conditions. The most common selection statement in Python is the if statement.

• if: Executes a block of code if a condition is True.

• elif: Checks another condition if previous if was False.

• else: Executes if all previous conditions are False.

Return statement is used in functions to send a value back to the caller.

Example:

• Python code: if x > 5: return 'Greater'

Functions: Definitions and Calling

A function is a reusable block of code that performs a specific task. Functions are defined using the def keyword in Python.

• Definition: def functionName(parameters):

• Calling: functionName(arguments)

Example:

• Defining a function: def add(a, b): return a + b

• Calling the function: add(2, 3) returns 5

Testing: Developing Test Cases

Test cases are specific inputs and expected outputs used to verify that a function works correctly. Good test cases cover normal, boundary, and edge cases.

• Test case example for a function calculateDamage(10, 4): Expected output is 4.

Function Implementation Examples

calculateDamage Function

This function models a simple game mechanic where two integers represent an attack roll and potential damage. The function returns damage based on the roll.

• Definition: def calculateDamage(attack, damage):

• If attack > 15: Return 2 × damage

• Else if attack >= damage: Return damage

• Else: Return 0

Test Cases:

• calculateDamage(10, 4) returns 4

• calculateDamage(8, 4) returns 0

• calculateDamage(20, 6) returns 12

checkForEven Function

This function checks if any of three integer parameters are even and returns a string indicating which are even, or 'All even!' if all are even.

• Definition: def checkForEven(a, b, c):

• If any parameter is even, return a string like 'X is odd' for odd values.

• If all are even, return 'All even!'

Test Cases:

• checkForEven(10, 12, 14) returns 'All even!'

• checkForEven(10, 12, 13) returns '13 is odd'

isBetween Function

This function checks if a value falls between two other values (inclusive).

• Definition: def isBetween(a, b, c):

• Returns True if c is between a and b (inclusive), else False.

Test Cases:

• isBetween(4, 10, 6) returns True

• isBetween(4, 10, 14) returns False

goodSteak Function

This function uses the isBetween function to determine if a steak's temperature is 'Perfect' or not.

• Definition: def goodSteak(temp):

• If temp is between 130 and 135 (inclusive), return 'Perfect'

• Else, return 'Oops...try again!'

Test Cases:

• goodSteak(132) returns 'Perfect'

• goodSteak(130) returns 'Perfect'

• goodSteak(150) returns 'Oops...try again!'

describePerson Function

This function classifies a person based on age into categories: child, teenager, adult, senior, or 'probably dead'.

• Definition: def describePerson(age):

• If age ≤ 12: return 'child'

• If 13 ≤ age ≤ 19: return 'teenager'

• If 20 ≤ age ≤ 59: return 'adult'

• If 60 ≤ age ≤ 99: return 'senior'

• If age ≥ 100: return 'probably dead'

Test Cases:

• describePerson(10) returns 'child'

• describePerson(19) returns 'teenager'

• describePerson(27) returns 'adult'

• describePerson(90) returns 'senior'

• describePerson(105) returns 'probably dead'

Summary Table: Function Purposes and Test Cases

Submission Instructions

• Save your main Python file as main.py.

• Submit to the designated platform before the due date.

• Final submission is due Monday, Sep 29 at 8:00PM.

Additional info: While the assignment is focused on Python programming, the logical structure and use of selection statements are directly applicable to mathematical modeling and problem-solving in Precalculus.