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for c in 'ROSE': Good Code For each value of the control variable c in the
if c == 'O': O string 'ROSE', the if-else statement is
print(c) Good Code executed.
else: Good Code
print('Good Code')
for c in 'ROSE': O For each value of the control variable c in the
if c == 'O': Good Code string 'ROSE' the if statement is executed.
print(c) The else clause is part of the for statement,
else: and it is executed after all iterations of the for
print('Good Code') statement have been completed.
6.4 while Statement
The while statement is used to execute a sequence of statements over and over again as long as the condition
specified in the while statement is True. The sequence of statements that is executed repeatedly is called body of
the while statement. The while statement has the following syntax:
while test condition:
Body of while loop
[else:
Statements]
In the above syntax description:
• while is a keyword.
• test condition is the expression that will evaluate to either True or False.
• body of while loop constitutes the statement(s) that will be executed if the test condition is True. These are
determined through indentation. The first un-indented line marks the end of the loop.
• else (optional) is a keyword and the statements in else block (optional) will be executed after all the possible
iterations of the while loop are executed.
We first discuss the while statement, ignoring the optional else clause. Fig 6.2 shows a flowchart that depicts
the execution of such a while statement. Note that the Boolean expression (also called a conditional expression,
test expression, or just a condition) in the while statement is evaluated before the body of the while statement
is executed. If the Boolean expression yields False, the loop's body is skipped, and the execution of the while
statement ends. However, if the Boolean expression yields True, the body of the while statement is executed. On
executing the loop's body, the Boolean expression is evaluated again. If the Boolean expression yields True, the
loop's body is executed again. This process of evaluating the Boolean expression and executing the body of the while
statement is repeated until the Boolean expression becomes False.
Enter while loop
Test False
Expression
True
Body of
while
Exit loop
Fig 6.2: while statement
Looping in Python 135

