# Python Loops

Python Loops, Python Control flow statements in Python, Python for loop, Python while loop, and Python nested loop structures.

## Python Language Loops

In general, statements are executed sequentially in Computer programming,

Programming languages provide various control structures that allow for more
complicated execution paths.

A loop statement allows us to execute a statement or group of statements multiple times.

Python programming language provides two loop structures,

1. while loop
2. for loop to handle loop requirements…

### 1. while loop

It repeatedly executes statements while condition is true…

Syntax:

while (condition/expression):
statement(s);

Example 1 – Print 1 to 10 Numbers.

a=1;
while (a<=10):
print(a);
a=a+1;
Output:
1
2
3
4
5
6
7
8
9
10

Example 2: Read a Number, and calculate sum, and Zero to quit from the loop

a=1;
sum=0;

print (“Enter a Number to add to the sum: “);
print (“Enter 0 to quit.”);

while a != 0:
print (“Current Sum: “, sum);
a= float(input(“Enter Number: “));
a=float(a);
sum += a;
print(“Total Sum is: “, sum);

Example 3: Print 1 to 5 Numbers in reverse order…

val=5;
while (val >= 1):
print(val);
val = val-1;

Output:

5
4
3
2
1

Example 4: Print 1 to 10 Numbers in reverse orderâ€¦

i=10;
while (i>=1):
print(i);
i=i-1;

Example 5: Print 1 to 10 Numbers except 4th Order

i=1;
while (i<=10):
if (i!=4):
print(i);
i=i+1;

### 2. for loop

for loop iterates over the items of any sequence, such as a list or a string.

Syntax:

for iterating_var in sequence:
statement(s);

Example 1:
a= [2, 4, 6, 8, 10, 12, 14];

for num in a:
print(num);

Output:
2
4
6
8
10
12
14
————————
Example 2:
for num in range(5):
print(num);

output:
0
1
2
3
4

Example 3: Print 1 to 10 Numbers

for num in range(1, 11):
print(num);

Example 4: Print 10 to 1 Numbers

for i in range(10, 0,-1):
print (i)

Example 5: Print 1 to 10 Numbers except 7th Number

for i in range(1, 11):
if (i !=7):
print (i)

Example 6: Print even numbers up to 10

for i in range(2, 11, 2):
print (i)

Note: If you do need to iterate over a sequence of numbers, the built-in function range() comes in handy. It generates arithmetic progressions.

Note: we can use conditional statements only in our script, or loop statements only, or we can insert loops in Conditional statements and vice versa.