4.2 The while Loop

Example

while loop for Fibonacci Numbers

Fibonacci Numbers: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, …

The first two terms are 1 and 1. All other terms are obtained by adding the preceding two terms.

Below is a code that lists Fibonacci numbers up to a user given count.

# type in the number of Fibonacci number you want to list and press enter.
# n = input("How many Fibonacci numbers? Type a number and press enter. ")
n = "5"   # ← web edition: the value the book's own run typed in

n = int(n)              # convert it to an integer

i = 0                   # set i to zero initially
a = 1                   # first number is 1
b = 1                   # second number is 1  

while i < n:            # i starts at zero and ends at n-1 
    print (a)
    i = i + 1
    c = a + b          # sum assigned to c
    a = b              # second assigned to first
    b = c              # sum assigned to second

How many Fibonacci numbers? Type a number and press enter. 5
1
1
2
3
5

Lab 4.2.1

List the first 20 Fibonacci numbers.

view answer

Lab 4.2.2

Write a Python code that lists all positive integers starting from 1 till a user given number.

view answer

Adapted from Python for Introductory Statistics: Student's Lab Workbook, by Simon Aman (Truman College, City Colleges of Chicago), licensed under CC BY 4.0. Changes were made: reformatted as an accessible XYZ web edition with live in-browser code cells. License: CC-BY-4.0.