For Loop Statements in Python

Hello dear readers! Welcome back to another edition of our tutorial on Python. In this tutorial guide, we are going to be discussing about the Python for Loop Statements.

For Loop statement has the ability to iterate over the items of any of the sequence, such as a list or a string.

Syntax

The syntax for a Python for Loop statement is as follows -

for iterating_var in sequence:
   statements(s)

If a sequence holds an expression list, then it is first evaluated. The first item in the sequence would then be assigned to the iterating variable iterating_var. Next, the statements block will be executed. Each item in the list is going to be assigned to the iterating_var, and the statement(s) block is going to be executed until entire sequence is exhausted.

Flow Chart

RECOMMENDED: Python While Loop Tutorial with examples 

Example

Below is a very short example -

#!/usr/bin/python

for letter in 'Python':     # First Example
   print 'Current Letter :', letter

fruits = ['banana', 'orange',  'apple']
for fruit in fruits:        # Second Example
   print 'Current fruit :', fruit

print "Welcome to Web design tutorialz!"

Output

The following below is the output of the above example -

Current Letter : P
Current Letter : y
Current Letter : t
Current Letter : h
Current Letter : o
Current Letter : n
Current fruit : banana
Current fruit : orange 
Current fruit : apple
Welcome to Web design tutorialz!

Iterating by Sequence Index 

An alternative means which can be used to iterate through the items is by index offset into the sequence it self.

Example

The following below is a simple example -

#!/usr/bin/python

fruits = ['banana', 'orange',  'apple']
for index in range(len(fruits)):
   print 'Current fruit :', fruits[index]

print "Welcome to Web design tutorialz!"

Output

The following below is the output of the above example -

Current fruit : banana
Current fruit : orange
Current fruit : apple
Welcome to Web design tutorialz!

Here, we took the help of the len() built-in function, that provides the total number of elements in the tuple and range() built in function to give us the actual sequence to be iterated over.

RECOMMENDED: Loop Control Statements in Python Programming

Using else Statement with Loops

Python has support for the feature of having an else statement associated with a loop statement.

• If the else statement is used with a for loop, the else statement will be executed when the loop has finished iterating the list.

• If the else statement is used with a while loop, then the else statement is going to be executed as soon as the condition returns false.

Example

The example that we have  below illustrates the combination of an else statement with a for loop statement that searches for the prime numbers from 10 through 20.

#!/usr/bin/python

for num in range(10,20):     #to iterate between 10 to 20
   for i in range(2,num):    #to iterate on the factors of the number
      if num%i == 0:         #to determine the first factor
         j=num/i             #to calculate the second factor
         print '%d equals %d * %d' % (num,i,j)
         break #to move to the next number, the #first FOR
   else:                  # else part of the loop
      print num, 'is a prime number'

Output

The following below is the output of the above example -

10 equals 2 * 5
11 is a prime number
12 equals 2 * 6
13 is a prime number
14 equals 2 * 7
15 equals 3 * 5
16 equals 2 * 8
17 is a prime number
18 equals 2 * 9
19 is a prime number

Alright guys! This is where we are rounding up for this tutorial. In our next tutorial, we will be discussing about the Python nested Loops.

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