Understanding Loops in Python

Loops are a fundamental concept in programming that allow you to repeat a specific block of code. In Python, there are two main types of loops: for and while.

while Loop

The while A loop in Python is used to repeatedly execute a block of code as long as the test expression (or condition) evaluates to True.

Syntax:

while test_expression:
   # body of while loop

In a while In a loop, the condition is evaluated before each iteration. The body of the loop is executed only if the condition is True. After each iteration, the condition is checked again. This continues until the condition evaluates to False.

The body of the while the loop is defined by indentation. The block of code inside the loop starts with an indented line, and the loop ends when the indentation is no longer present.

Example:

i = 1
while i < 6:
   print(i)
   i += 1

Output:

1
2
3
4
5

In this example, the loop continues as long as i it is less than 6. The variable i is incremented with each iteration. If we forget to increment i, the loop will run indefinitely, creating an infinite loop.

while Loop with else

A while the loop can also have an optional else block. This block is executed when the condition evaluates to False.

Example:

i = 1
while i < 6:
   print(i)
   i += 1
else:
   print("i is no longer less than 6")

Output:

1
2
3
4
5
i is no longer less than 6

Here, when i At 6, the condition becomes False, and the else the block is executed.

for Loop

A for the loop is used to iterate over a sequence (like a list, tuple, or string) or any other iterable object.

Syntax:

for variable in sequence:
   # body of for loop

The loop will continue until all items in the sequence are processed. As with the while loop, the body of the for the loop is determined by indentation.

Example:

for x in "programming":
   print(x)

Output:

p
r
o
g
r
a
m
m
i
n
g

range() Function

To loop through a block of code a specific number of times, the range() function can be used. It generates a sequence of numbers, starting from 0 by default and incrementing by 1 (unless specified otherwise), ending before a given number.

Example:

for x in range(7):
   print(x)

Output:

0
1
2
3
4
5
6

Note that range(7) generates numbers from 0 to 6, not 0 to 7.

You can also specify a starting point and an increment. For example, range(3, 7) will generate values from 3 to 6 (but not including 7).

Example:

for x in range(3, 7):
   print(x)

Output:

3
4
5
6

To change the increment value, you can add a third parameter. For instance, range(1, 10, 2) will increment by 2:

Example:

for x in range(1, 10, 2):
   print(x)

Output:

1
3
5
7
9

else in for Loop

In a for loop, the else keyword specifies a block of code to be executed when the loop completes all iterations, without encountering a break statement.

Example:

for x in range(5):
   print(x)
else:
   print("Finished Counting!")

Output:

0
1
2
3
4
Finished Counting!

In this example, the loop prints all the numbers from 0 to 4, and then the else the block is executed, printing the message "Finished Counting!".