Computer Programming CSC 1401 PDF

Computer Programming CSC 1401 Instructor: Dr. Oumaima Hourrane Email: [email protected] School of Science and Engineering Module 4 Basic Data Concepts 2 Data types Data Manipulation: Programs process various forms of information. Different Forms of Data:...

Computer Programming CSC 1401 Instructor: Dr. Oumaima Hourrane Email: [email protected] School of Science and Engineering Module 4 Basic Data Concepts 2 Data types Data Manipulation: Programs process various forms of information. Different Forms of Data: Text (e.g., names, addresses) Numbers (e.g., age, salary) Dates and Times What is a Data Type? A category of data values that are related. Defines the operations that can be performed on the data. Computer Programming - CSC 1401 3 Data types in Python Automatic Type Inference: Python determines the data type based on the value. Computer Programming - CSC 1401 4 Data types in Python - Numeric Types Integers (int): Whole numbers without a decimal point. Stored exactly in memory. Suitable for counts, indices, and discrete quantities. Examples: -10, 0, 25, 1024 Floating-Point Numbers (float): Real numbers with a decimal point. Used for measurements, calculations requiring fractions. Examples: 3.1415, 0.0, -2.718 Computer Programming - CSC 1401 5 Expressions in Python An expression is a combination of values and operations that evaluates to a result. ➔ Simple Expressions: Literal values like 42 or 3.14. ➔ Complex Expressions: Calculations like (2 * 6) + (4 * 4) + 2. Components: Operands: The values (e.g., 2, 6). Operators: The symbols denoting operations (e.g., *, +). Computer Programming - CSC 1401 6 Evaluating Expressions Order of Operations: 1. Parentheses () 2. Exponents ** 3. Multiplication * and Division / 4. Addition + and Subtraction - Using Parentheses: Clarifies the intended order. Ensures accurate calculations. Example: result = (2 * 6) + (4 * 4) + 2 print(result) # Output: 34 Computer Programming - CSC 1401 7 Practical Question If you have: ○ Three packs of 5 items. ○ Five individual items. How many items do you have in total? Take a moment to write the expression and calculate the result. Computer Programming - CSC 1401 8 Practical Question Solution If you have: ○ Three packs of 5 items. ○ Five individual items. How many items do you have in total? Take a moment to write the expression and calculate the result Expression: total_items = (3 * 5) + 5 print(total_items) # Output: 20 Computer Programming - CSC 1401 9 Expressions - Operators and Operands Operator: A special symbol used to indicate an operation. Examples: +, -, *, / Operand: The values that operators act upon. Can be literals, variables, or other expressions. Example: 3 + 29 4*5 Computer Programming - CSC 1401 10 Practice Question Evaluate the expression without typing it into Python: (5 * 3) + (12 / 4) - 7 A) 11 B) 12 C) 13 D) 14 11 Practice Question Solution Evaluate the expression without typing it into Python: (5 * 3) + (12 / 4) - 7 A) 11 Calculations: B) 12 - (5 * 3) → 15 C) 13 - (12 / 4) → 3.0 D) 14 - 15 + 3.0 - 7 → 11.0 12 Literals Definition: A direct value in code. Integer Literals (int): 3, 482, -29434, 0 Float Literals (float): 298.4, 0.284, 207. (207.0),.2843 (0.2843). 2.3e4 → 23000.0 1e-5 → 0.00001 String Literals (str): 'abc', "hello", "I'm happy!", Empty string " " or ' ' Boolean Literals (bool): True, False Computer Programming - CSC 1401 13 Arithmetic Operators Computer Programming - CSC 1401 14 Arithmetic Operators - Mod operator Examples of % Mod Operator Computer Programming - CSC 1401 15 Special Cases with Division and Modulus Numerator Smaller than Denominator: Division: Result is 0. Modulus: Result is the numerator. Example: 7 // 10 # Output: 0 7 % 10 # Output: 7 Numerator is Zero: Both division and modulus return 0. Denominator is Zero: Results in a runtime error (ZeroDivisionError). Computer Programming - CSC 1401 16 Practice Question What is the output of the following code? print(20 % 3) print(20 // 3) A) 2 and 6 B) 1 and 6 C) 2 and 6.666... D) 1 and 6.666... 17 Practice Question Solution What is the output of the following code? print(20 % 3) print(20 // 3) A) 2 and 6 Calculation: B) 1 and 6 - 20 % 3 → Remainder of 20 / 3 → 2 C) 2 and 6.666… - 20 // 3 → Quotient of 20 / 3 without remainder → 6 D) 1 and 6.666... 18 Operator Precedence in Python Order of Operations: 1. Parentheses () 2. Exponentiation ** 3. Unary operators +, - 4. Multiplicative operators *, /, //, % 5. Additive operators +, - Remember: PEMDAS: Parentheses, Exponents, Multiplication/Division, Addition/Subtraction. Computer Programming - CSC 1401 19 Unary Operators Definition: Operators that act on a single operand. Examples: Unary Plus: +5 (no effect) Unary Minus: -8 (negates the value) Precedence: Higher than multiplicative operators. Example: 12 * -8 # Output: -96 Computer Programming - CSC 1401 20 Evaluating Complex Expressions Expression: 13 * 2 + 239 // 10 % 5 - 2 * 2 Steps: 1. Multiplications and Divisions: ○ 13 * 2 → 26 ○ 239 // 10 → 23 ○ 23 % 5 → 3 ○ 2*2→4 2. Additions and Subtractions: ○ 26 + 3 → 29 ○ 29 - 4 → 25 Result: The expression evaluates to 25. Computer Programming - CSC 1401 21 Mixing and Converting Types Implicit Conversion: Python automatically converts int to float when necessary. Example: 2 * 3.6 # Output: 7.2 (float) Explicit Conversion: Using int() and float() functions. Syntax: int(expression) float(expression) Computer Programming - CSC 1401 22 Type Conversion Examples Converting Float to Int: Truncates decimal part (does not round). Examples: int(4.75) # Output: 4 int(17.3) # Output: 17 int(3.14159) # Output: 3 Converting Int to Float: Adds a decimal point. Example: float(42) # Output: 42.0 Computer Programming - CSC 1401 23 Practice Question What is the result of the following code? result = int(5.99) + float(2) print(result) A) 7.99 B) 7.0 C) 8.0 D) 7 24 Practice Question Solution What is the result of the following code? result = int(5.99) + float(2) print(result) A) 7.99 Calculations: B) 7.0 - int(5.99) → 5 C) 8.0 - float(2) → 2.0 D) 7 - 5 + 2.0 → 7.0 (since one operand is float, result is float) 25 Summary Expressions: Combinations of operands and operators. Evaluated according to precedence rules. Operators: Arithmetic operators perform mathematical operations. Operator precedence affects evaluation order. Literals: Directly represent values in code. Include integers, floats, strings, booleans. Type Conversion: Implicit and explicit conversions between types. Use int() and float() for explicit conversion. Computer Programming - CSC 1401 26 Module 4 Variables 27 What is a Variable? Variable: A named location in memory that stores a value. Think of a variable as a container that holds data. Allows us to store, retrieve, and manipulate data in our programs. Computer Programming - CSC 1401 28 Why Use Variables? Avoid Redundancy: Store values that are used multiple times. Simplify code maintenance and readability. Flexibility: Easily change values in one place. Variables can be updated as the program runs. Computer Programming - CSC 1401 29 Defining Variables in Python Syntax: variable_name = expression Assignment Operator = : Evaluates the expression on the right. Stores the result in the variable on the left. Computer Programming - CSC 1401 30 Variable Naming Rules Must start with: A letter (a-z, A-Z) Or an underscore _ Can contain: Letters, digits (0-9), underscores Cannot contain: Spaces Special characters (e.g., !, @, #, $) Case-sensitive: age and Age are different variables. Computer Programming - CSC 1401 31 Variable Naming Conventions Use descriptive names: Good: subtotal, number_of_items Bad: x, y, z (unless context is clear) Use lowercase letters: Separate words with underscores: total_price, average_age Avoid using Python keywords: Such as print, def, if, else Computer Programming - CSC 1401 32 Examples of Variable Definitions Simple Assignment: subtotal = 30 + 22 + 17 + 46 Using Variables in Expressions: tax_rate = 0.1 taxes = subtotal * tax_rate total = subtotal + taxes Computer Programming - CSC 1401 33 Using Variables in Expressions Variables can be used in place of values: Once defined, they can be used in any expression. Example: subtotal = 115 print("Subtotal:", subtotal) print("Taxes:", subtotal * 0.1) print("Total:", subtotal * 1.1) Computer Programming - CSC 1401 34 Updating Variable Values Variables can be reassigned: weight = 195 weight = 180 # Updated value Important: Updating a variable does not automatically update other variables that depended on the old value. Computer Programming - CSC 1401 35 Incrementing and Decrementing Variables Incrementing: Increasing the value by a certain amount. Example: x = x + 1 # Increases x by 1 Decrementing: Decreasing the value by a certain amount. Example: y = y - 1 # Decreases y by 1 Computer Programming - CSC 1401 36 Shorthand Assignment Operators Simplify incrementing/decrementing: x += 1 is equivalent to x = x + 1 y -= 1 is equivalent to y = y - 1 Other Operators: *= for multiplication: x *= 2 (doubles x) /= for division: y /= 3 (divides y by 3) //= for integer division %= for modulus Computer Programming - CSC 1401 37 Practical Example: Basal Metabolic Rate (BMR) Formula for Men: bmr_male = 4.54545 * weight + 15.875 * height - 5 * age + 5 Formula for Women: bmr_female = 4.54545 * weight + 15.875 * height - 5 * age - 161 Variables Needed: weight in kilograms height in centimeters age in years Computer Programming - CSC 1401 38 Code Example: Calculating BMR # Define variables height = 70 # in inches weight = 195 # in pounds age = 40 # in years # Convert to metric units if necessary height_cm = height * 2.54 # inches to centimeters weight_kg = weight * 0.453592 # pounds to kilograms # Calculate BMR bmr_male = 4.54545 * weight_kg + 15.875 * height_cm - 5 * age + 5 bmr_female = 4.54545 * weight_kg + 15.875 * height_cm - 5 * age - 161 # Print results print("BMR for Male:", bmr_male) print("BMR for Female:", bmr_female) Computer Programming - CSC 1401 39 Code Example: Calculating BMR # Define variables height = 70 # in inches weight = 195 # in pounds age = 40 # in years # Convert to metric units if necessary height_cm = height * 2.54 # inches to centimeters weight_kg = weight * 0.453592 # pounds to kilograms # Calculate BMR bmr_male = 4.54545 * weight_kg + 15.875 * height_cm - 5 * age + 5 bmr_female = 4.54545 * weight_kg + 15.875 * height_cm - 5 * age - 161 # Print results print("BMR for Male:", bmr_male) print("BMR for Female:", bmr_female) Computer Programming - CSC 1401 40 Variable Reassignment Example Scenario: A person loses weight from 195 lbs to 180 lbs. Update Variable: weight = 180 # Update weight variable Recalculate BMR: weight_kg = weight * 0.453592 bmr_male = 4.54545 * weight_kg + 15.875 * height_cm - 5 * age + 5 print("Updated BMR for Male:", bmr_male) Computer Programming - CSC 1401 41 Important Note on Variable Reassignment Changing a variable does not automatically update other variables. Example: After weight is updated, bmr_male must be recalculated. Why? Variables store values, not formulas. Computer Programming - CSC 1401 42 Printing Multiple Values Using Commas: print("Your BMR is", bmr_male) Output: Your BMR is 1802.61275 Multiple Variables: print("Height:", height, "inches", "Weight:", weight, "pounds") Computer Programming - CSC 1401 43 Formatting Output Default Separator: Comma-separated values are printed with spaces. Custom Separator: print("Date:", year, month, day, sep="/") Output: Date:2021/1/20 Computer Programming - CSC 1401 44 Practical Question 1 Write code to calculate the total cost of items with a 10% tax rate. Items cost: $30, $22, $17, $46 Tasks: 1. Calculate the subtotal. 2. Calculate the taxes. 3. Calculate the total. 4. Print all results. Computer Programming - CSC 1401 45 Practical Question 2 Question: A person's age is 28. Calculate how many years until they turn 65. Print a message: "You will retire in X years." Task: Use variables and appropriate calculations. Computer Programming - CSC 1401 46 Practical Question 3 1. Define variables x = 10 and y = 5. 2. Increment x by 3 using shorthand operator. 3. Decrement y by 2 using shorthand operator. 4. Multiply x and y and print the result. Computer Programming - CSC 1401 47 Summary Variables store values for later use. Assignment uses the = operator. Variable names should be descriptive and follow naming rules. Variables can be updated, but dependent variables need to be recalculated. Printing allows multiple values and custom formatting. Computer Programming - CSC 1401 48  Q&A ⁉ For Further questions and inquiries please reach out! ([email protected]) Office Hours: MWF 1 pm to 2 pm Office Place: Bldg 8B, Room 205 49