Loops in Python

The Python programming language provides the following types of loops to handle looping requirements. Python offers three methods for executing loops. Although all methods offer the same basic functionality, they differ in their syntax and location check times.

Lets start

While loop:

In Python, loops are used to repeatedly execute a block of statements until a condition is satisfied. And when the situation is wrong, the line will run as soon as the loop in the program arrives.

Now we will see the Syntax

Syntax :

while (expression):
    statement(s)

All statements given the same number of character spaces after programming constructions are considered part of the same block code. Python uses indentation as a way to make its own statements.

Lets see this by an example

count = 1

while (count < 4):    

    count = count + 1

    print("Hello Dudle")




Output:




Hello Dudle

Hello Dudle

Hello Dudle










Using an else statement with while loops:

Executes the loop block until a condition is fulfilled, 

as discussed above. When the situation returns incorrectly, the statement as soon as the

loop is executed.The second condition applies only when your condition is incorrect.

If you exit the loop, or the exception is increased, it will not run.




Lets see by an example:

if (condition):

    # execute these statements in the block

else:

    # execute these statements in the block

Lets see the while loop:

while (condition):

     # execute these statements in the block

else:

     # execute these statements in the block

Lets see the combining part:

# combining else part with the while loop

count = 1

while (count < 4):    

    count = count + 1

    print("Hello Dudle")

else:

    print("comes to Else Block")







Output:

Hello Dudle

Hello Dudle

Hello Dudle

Comes to Else Block







While Block with single statement:




If the block contains the same statement as I did, the whole loop can be declared in

one line as shown below:

# while block with single statement

count = 1

while (count == 1): print("Hello Geek")




Note:




It is advisable not to use these types of loops, as this is an infinite loop that never ends, where the situation is always correct and you must end the compiler. See this for an example of using a loop for iterations. As mentioned in the article, it is not recommended to use loops for iterations in Python.

For loops:

Used for row traversal for loops. For example: Detecting list or string or array In Python, there is no C style for loops, i.e. (i = 0; i <n; i ++). The loop contains "for", which is the same for each loop in other languages. Let's learn how to use loop for sequential travels.




Lets see the Syntax:

for iterator_variable in range:
    statements(s)




# Iterating over range 0 to n-1

  

n = 5

for i in range(0, n):

    print(i)







Output :




0

1

2

3

4




Lets see some other codes




# Iterating over a list for this

print("List Iteration")

l = ["code", "for", "dudle"]

for i in l:

    print(i)

       

# Iterating over a tuple (immutable)

print("Tuple Iteration\n")

t = ("code", "for", "dudle")

for i in t:

    print(i)

       

# Iterating over a String

print("String Iteration\n")    

s = "code"

for i in s :

    print(i)

       

# Iterating over dictionary

print("Dictionary Iteration\n")   

d = dict() 

d['xyz'] = 124

d['abc'] = 344

for i in d :

    print("%s  %d" %(i, d[i]))







Output:

List Iteration

geeks

for

geeks

Tuple Iteration

geeks

for

geeks

String Iteration

c

o

d

e

Dictionary Iteration

xyz  124

abc  344

Iterating Changes by index of sequence: We can also use the index of elements in an order. The main idea is to first calculate the list length and then redirect it over the order of this length range.

See examples below:

# Iterating by index sequence

  

list = ["code", "dudle"]

for index in range(len(list)):

    print list[index]




Output :




code

dudle




Using else statement with the for loops:

Other statements in the loop can also be included in the loop. Since there are no

conditions for the loop based on which execution ends, any other block will be

executed after the block finishing execution.

The following examples show how to do this:

# combining else part with for looping

  

list = ["code", "dudle"]

for index in range(len(list)):

    print list[index]

else:

    print "Inside the Else Block"




Output:




code

dudle

Inside the Else block




We can use loop‌ for user-defined iterations. See this for example.

Nested loops:

Python programming language allows to use one loop inside

another loop. The following concept shows some examples to illustrate

the concept.

Syntax:




for iterator_variable in sequence:

    for iterator_variable in sequence:

        statements(s)

        statements(s)







Now the nested while loop

while expression:

    while expression: 

        statement(s)

        statement(s)




The last note on the loop niche here is that we can place any type of loop inside

another type of loop. For example for loop the loop may be within a while or vice versa.




Lets see by an example:




# nested for loops in Python

from __future__ import print_function

for i in range(1, 6):

    for j in range(i):

         print(i, end=' ')

    print()




Output :




1

22

333

4444

55555




Loop Control Statement:




The loop control statement replaces the execution from its normal sequence. When

the execution leaves a scope, all automated objects created within that scope are

destroyed.




Python supports the following control statements.




# Prints all letters except 'o' and 'u' for letter in 'codedudle': if letter == 'o' or letter == 'u': continue print 'Current Letters are :', letter var = 8

Output

Current Letters are : c Current Letters are : d Current Letters are : e Current Letters are : d Current Letters are : d Current Letters are : l Current Letters are : e

Break Statement:

It brings the control out of the loop and stop the execution for letter in 'codedudle': if letter == 'o' or letter == 'u': break print 'Current Letter are:', letter Output:

Current Letter are: o

Pass statement: We use pass statement to write a blank loop. Pass space control is also used

for announcements, functions and classes.

for letter in 'codedudle': pass print 'Last Letter are :', letter

Output : Last Letter are : e In this article i have explained the looping syntax in python.

Recommended :

• Techniques of Looping
• Operators in Python
• Ternary Operator with examples in Python
• Any and All in Python
• Inplace and Standard operator in python
• Python a += b is not always a = a + b
• Difference between == and is operator
• Python Membership and Identity Operators