In Python, a loop is a programming construct that allows you to repeat a block of code multiple times. There are two types of loops in Python: for loop and while loop.
For loop
A for loop is used to iterate over a sequence (e.g., a list, tuple, dictionary, or string) and execute a block of code for each item in the sequence. Here’s the basic syntax of a for loop in Python:
for item in sequence:
# code to be executed
Here’s an example that uses a for loop to print the numbers from 1 to 5:
for i in range(1, 6):
print(i)
Output:
1
2
3
4
5
In the example above, the range() function generates a sequence of numbers from 1 to 5 (inclusive) and the for loop iterates over each number in the sequence and prints it.
While loop
A while loop is used to execute a block of code repeatedly as long as a certain condition is true. Here’s the basic syntax of a while loop in Python:
while condition:
# code to be executed
Here’s an example that uses a while loop to print the numbers from 1 to 5:
i = 1
while i <= 5:
print(i)
i += 1
Output:
1
2
3
4
5
In the example above, the while loop iterates over the numbers from 1 to 5 as long as i is less than or equal to 5. The loop starts with i equal to 1, prints the value of i, increments i by 1, and repeats the process until i becomes 6, at which point the loop stops.
Loops are a fundamental building block of programming, and they allow you to write more efficient and concise code by automating repetitive tasks.
Here are some more examples of loops in Python:
Example 1: Printing the elements of a list using a for loop
fruits = ["apple", "banana", "orange", "grape"]
for fruit in fruits:
print(fruit)
Output:
apple
banana
orange
grape
In the example above, the for loop iterates over each item in the fruits list and prints it.
Example 2: Calculating the sum of a list using a for loop
numbers = [1, 2, 3, 4, 5]
sum = 0
for number in numbers:
sum += number
print("The sum is:", sum)
Output:
The sum is: 15
In the example above, the for loop iterates over each item in the numbers list and adds it to the sum variable.
Example 3: Printing the numbers from 1 to 10 using a while loop
i = 1
while i <= 10:
print(i)
i += 1
Output:
1
2
3
4
5
6
7
8
9
10
In the example above, the while loop iterates over the numbers from 1 to 10 as long as i is less than or equal to 10. The loop starts with i equal to 1, prints the value of i, increments i by 1, and repeats the process until i becomes 11, at which point the loop stops.
