Python Devlopment



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for loop

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Python For Loops

A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).

This is less like the for keyword in other programming language, and works more like an iterator method as found in other object-orientated programming languages.

With the for loop we can execute a set of statements, once for each item in a list, tuple, set etc.

#Print each fruit in a fruit list:
marks = [10,20,30,40,50]
for x in marks:
    print(x)

The break Statement

With the break statement we can stop the loop before it has looped through all the items:

#Exit the loop when x is 30:
marks = [10,20,30,40,50]
for x in marks:   
    print(x)   
if x == 30:     
    break

Output:     
10
20
30

Example 2:

    Exit the loop when x is 30, but this time the break comes before the print:

marks = [10,20,30,40,50]
for x in marks:   
    if x == 30:    
        break   
    print(x)

Output:     
10    
20

The continue Statement

With the continue statement we can stop the current iteration of the loop, and continue with the next:

#Do not print banana:
marks = [10,20,30,40,50]
for x in marks:   
    if x == 30:     
        continue   
    print(x)

Output:    
10    
20        
40    
50

Nested Loops

A nested loop is a loop inside a loop. The "inner loop" will be executed one time for each iteration of the "outer loop":

Example:1

#Print each adjective for every fruit:
adj = ["red", "big", "tasty"]
fruits = ["apple", "banana", "cherry"]
for x in adj:   
    for y in fruits:     
         print(x, y)

Output:
red apple
red banana
red cherry
big apple
big banana
big cherry
tasty apple
tasty banana
tasty cherry

Example 2:

m1 = [1,2,3]
m2 = [10,20,30]
for x in m1:
    for y in m2:         
        print(x, y)

Output:     
(1, 10)
(1, 20)
(1, 30)
(2, 10)
(2, 20)
(2, 30)
(3, 10)
(3, 20)
(3, 30)