Page 66 - Code & Click - 8

7 Iterative Statements in Python

Pre-Processing
Pre-Processing
• Iterative Statements • Components of a Loop
• For Loop • Use of Range( ) function in For Loop
• While Loop • Jump Statements in a Loop in Python

The statements or instructions in a program or software are executed in a sequential manner. But
sometimes it is necessary to disrupt the sequential execution of statements and divert the execution
control to some other part of the program. Statements that are used to control the flow of execution
of statements in a program are called Control Statements. These are usually of two types:
• Selection Statements • Iterative Statements
You have learned about Selection statements, or Decision Control statements, in Python. Let’s now
learn about Iterative statements in Python.

ITERATIVE STATEMENTS
Sometimes, a set of instructions needs to be executed a number of times based on a specific
condition. Iterative statements are statements that are executed a specified number of times or
until a specified condition is True. Iterative statements are also called Loops.

COMPONENTS OF A LOOP
The main components of a loop are:
• Initialisation of Control Variable: A control variable is usually a numeric variable that counts
the number of times the loop is executed. It is also known as a Counter. It is assigned an initial
value, which is incremented or decremented after every execution of the loop statements.
• Updation of Control Variable: This is the part of the loop where the counter variable is
incremented or decremented.

• Test Expression: This is usually an expression, containing relational operators, which is
evaluated to check if the loop is to be executed further or not. The loop execution continues
until the value of the test expression is True.

• Body of Loop: This is the set of statements that will be executed repeatedly.
Python provides two basic types of loops:
• For loop • While loop

FOR LOOP
The For loop is used when the number of times the loop is to be executed is known beforehand. That
is why the For loop is called a Definite loop. The syntax of the For loop is as follows:
for <counter variable> in <sequence>:
body of for loop
other statements

64