Part 4 - Python Flow Control

In Part 4, we will expand to discuss Python's flow control using Conditions and Loops.

Python Flow Control

Conditionals / decision making -  IF statement

For conditional flow control, use the if statement

• The  if header line ends with a colon (:)
• The statement block must be indented.
• elif means “else if”,
• elif is followed by a colon(:)
• else: execute the final statements    

      
This script uses the if -else statement, to decide if the value of x is greater than 5, then do this, otherwise(else) do that.

      

Loops

A loop is the iterative process of repeating of code lines. There are different types of loops such as  the For Loops, the While Loops and the Nested Loops.

Example of For Loop:

                 

                    

This script uses the FOR statement to repeat each item that is within the range of 10. Starting from 0 and up to(but not including) the last number 10. The default incrementing step is 1.

It will print the value for x from 0 to 10 for each of these value.

thus the result will be 0, 1, 2, 3, 4, 5, 6, 7,8, 9

Example of While Loop:

                  

This script uses the WHILE statement to repeat showing what the count is, and as long as the value of count is less than 9, it will show the count, then add one to count. Once count reaches 9, it will stop and do the next line, which is to show "Good bye!"

                   

Example of Nested Loop:  

                  

This script uses a series of nested loops to find out all the numbers between 2 and 100 that is prime.

It has a double nested while loop with a double if statement in it.

                   

Control Statements

Control statements are typically used together with the loops to complete the loop.

•          Break statement – to exit the loop (Loop_ForBreak_Prime.py)

•          Continue statement – jump to the top of the loop

•          Else statement – execute when condition is false.

•          Pass statement – command to do nothing.