Python Decision Structures and Looping: Exploring If, Else

University:
College
Course:
College Computer Science
Academic year:

2023
Views:

467

Pages:

23
Author:

priyankavaiya07

Module 2: Decision Structure in Python Outline • Conditional Blocks using If, Else and Else If • Simple for loops • For loop using ranges, String, List, and Dictionaries • Use of While loop • Loop Manipulation using Pass, Continue, Break and Else. Sequence statements • If statement • if-else statement • Nested if • If-elif statement Exercises • Program to check whether number is even or odd • Program to find largest among two numbers Assignment 1: Calculating Overtime Pay Nested if The for loop • for loop: Repeats a set of statements over a group of values. • Syntax: for variableName in groupOfValues: statements • We indent the statements to be repeated with tabs or spaces. • variableName gives a name to each value, so you can refer to it in the statements. • groupOfValues can be a range of integers, specified with the range function. • Example: for x in range(1, 6): print x, "squared is", x * x range • The range function specifies a range of integers: • range(start, stop) - the integers between start (inclusive) and stop (exclusive) • It can also accept a third value specifying the change between values. • range(start, stop, step) - the integers between start (inclusive) and stop (exclusive) by step • Example: for x in range(5, 0, -1): print x print "Blastoff!" Output: 5 4 3 2 1 Blastoff! • Exercise: How would we print the "99 Bottles of Beer" song? Cumulative loops • Some loops incrementally compute a value that is initialized outside the loop. This is sometimes called a cumulative sum. sum = 0 for i in range(1, 11): sum = sum + (i * i) print "sum of first 10 squares is", sum Output: sum of first 10 squares is 385 • Exercise: Write a Python program that computes the factorial of an integer. Looping Through a String • Strings are iterable objects, they contain a sequence of characters: Example: Output: Looping through List Example: Output: apple banana cherry Nested Loops • Nested loop is a loop inside a loop. • The “inner loop” will be executed one time for each iteration of the “outer loop” : Example: Print each adjective for every fruit: Output: while • while loop: Executes a group of statements as long as a condition is True. • good for indefinite loops (repeat an unknown number of times) • Syntax: while condition: statements • Example: number = 1 while number < 200: print number, number = number * 2 • Output: 1 2 4 8 16 32 64 128 Loop Manipulation • Pass • Continue • Break • Else The pass Statement • loops cannot be empty, but if you for some reason have a loop with no content, put in the pass statement to avoid getting an error. • Example: The break statement • Using break statement we can stop the loop before it has looped through all the items: Output: Apple banana The Continue Statement It is used to stop the current iteration of the loop, and continue with the next: Example: Output apple cherry Else in for loop • Else keyword in a for loop specifies a block of code to be executed when the loop is finished: • Example: print all numbers from 0 to 5, and print a message when the loop has ended: Output