Python Looping Statements
Table Of Contents:
- What Are Looping Statements?
- Types Of Looping Statements.
- while Loop.
- for Loop.
- Nested Loop.
(1) What Are Looping Statements?
- In the programming world, your code executes sequentially. That means, the first statement in a function is executed first, followed by the second, and so on.
- There will come a situation where you need to execute a block of code several times.
- At that time you can use, a python loop statement that will execute a statement or group of statements multiple times.
(2) Types Of Looping Statements?
- while loop
- for loop
- Nested Loop
(3) While Loop
- A while loop is used to execute a block of statements repeatedly until a given condition is satisfied.
- And when the condition becomes false, the line immediately after the loop in the program is executed.
While Loop Syntax
while condition:
Body Of While Loop.Example-1
count = 0
while (count < 9):
print('The count is:', count)
count = count + 1
print("Good bye!")Output:
The count is: 0
The count is: 1
The count is: 2
The count is: 3
The count is: 4
The count is: 5
The count is: 6
The count is: 7
The count is: 8
Good bye!Note:
- This While loop will execute till the count value is reaching to 8.
- It will execute 9 times, from 0 to 8.
Example-2
count = 0
while count < 6:
print(count, " is less than 6")
count = count + 1
else:
print(count, " is not less than 6")Output:
0 is less than 6
1 is less than 6
2 is less than 6
3 is less than 6
4 is less than 6
5 is less than 6
6 is not less than 6Note:
- Python supports having an else statement associated with a loop statement.
If the else statement is used with a while loop, the else statement is executed when the condition becomes false.
(4) For Loop
- For loops are used for traversing sequential variables like list, tuple, set, and dictionary.
- It will iterate over individual elements of a list, tuple, set, dictionary, or any sequence.
- The process of traversing a sequence is known as iteration.
- You can iterate over in both directions from front to back and from back to front.
For Loop Syntax
for value in sequence:
Body Of For Loop Example-1
numbers = [1,2,3,4,5]
for value in numbers:
print(value)Output:
1
2
3
4
5Note:
This program will iterate over a list element and print the values.
Example-2
message = "Hello World"
for i in message:
print(i)Output:
H
e
l
l
o
W
o
r
l
dNote:
This program will iterate over a string object and print the values.
(5) Nested Loops
- Python programming allows using one loop inside another loop.
- When you come across such a scenario, you can use Nested loops.
Nested Loop Syntax
for iterating_var in sequence:
for iterating_var in sequence:
statements(s)
statements(s)while expression:
while expression:
statement(s)
statement(s)Example-1
rows = int(input('Enter Number Of Rows'))
k = 0
for i in range(1,rows+1):
for space in range(1,(rows-i)+1):
print(end=" ")
while k != (2*i-1):
print("*",end=" ")
k += 1
k = 0
print()Enter Number Of Rows5
*
* * *
* * * * *
* * * * * * *
* * * * * * * * * Note:
This program will print a pyramid pattern using *.
Example-2
i = 2
while(i < 100):
j = 2
while(j <= (i/j)):
if not(i%j): break
j = j + 1
if (j > i/j) : print(i, " is prime")
i = i + 1
print("Good bye!")Output:
2 is prime
3 is prime
5 is prime
7 is prime
11 is prime
13 is prime
17 is prime
19 is prime
23 is prime
29 is prime
31 is prime
37 is prime
41 is prime
43 is prime
47 is prime
53 is prime
59 is prime
61 is prime
67 is prime
71 is prime
73 is prime
79 is prime
83 is prime
89 is prime
97 is prime
Good bye!Note:
This program will print all the prime numbers between 0 to 100.