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Beginner's Tutorial on For Loops ​

Introduction ​

Welcome to our beginner's tutorial on for loops in Python. For loops are very important in programming. They let you run a block of code many times, based on a sequence. This tutorial will give you a strong understanding of for loops. It will cover their structure, common uses, and key ideas you need to know.

Prerequisites ​

Before you start learning about for loops, it's important to know the basics of:

Variables and data types

Functions and basic syntax

Print statements

What is a For Loop? ​

A for loop controls the flow of a program. It lets you move through a sequence, such as a list, tuple, string, or range. For each item in the sequence, the for loop runs a block of code.

Syntax ​

Here's the basic syntax for a for loop in Python:

python
for item in sequence:  
    # Block of code to execute for each item  
    print(item)

Example 1: Iterating Over a List ​

php
fruits = ['apple', 'banana', 'cherry']  
  
for fruit in fruits:  
    print(fruit)

Output:

apple
banana
cherry

In this example, the for loop iterates over each item in the fruits list, and the print statement prints each fruit.

Example 2: Iterating Over a Range ​

The range() function in Python generates a sequence of numbers. You can use it with for loops to execute a block of code a specific number of times.

python
for i in range(5):  
    print(i)

Output:

0
1
2
3
4

In this example, the range(5) generates numbers from 0 to 4, and the for loop prints each number.

Example 3: Iterating Over a String ​

You can also use for loops to iterate over strings.

python
greeting = "Hello, World!"  
  
for char in greeting:  
    print(char)

Output:

H
e
l
l
o
,

W
o
r
l
d
!

In this example, the for loop iterates over each character in the greeting string, and the print statement prints each character.

Nested For Loops ​

You can nest for loops inside each other to create more complex iterations.

python
for i in range(3):  
    for j in range(2):  
        print(f"i = {i}, j = {j}")

Output:

i = 0, j = 0
i = 0, j = 1
i = 1, j = 0
i = 1, j = 1
i = 2, j = 0
i = 2, j = 1

In this example, the outer loop runs 3 times, and for each iteration of the outer loop, the inner loop runs 2 times.

Breaking and Continuing the Loop ​

You can use the break and continue statements to control the flow of the loop.

break: Terminates the loop and exits.
continue: Skips the current iteration and moves to the next.

Using break ​

python
for i in range(10):  
    if i == 5:  
        break  
    print(i)

Output: 0 1 2 3 4

Using continue ​

python
for i in range(10):  
    if i % 2 == 0:  
        continue  
    print(i)

Output: 1 3 5 7 9

Enumerate Function ​

The enumerate() function is useful when you need both the index and the value while iterating over a sequence.

fruits = ['apple', 'banana', 'cherry']

python
for index, fruit in enumerate(fruits):  
    print(f"Index: {index}, Fruit: {fruit}")

Output:
Index: 0, Fruit: apple
Index: 1, Fruit: banana
Index: 2, Fruit: cherry

Conclusion ​

Congratulations! You have finished the beginner's tutorial on for loops in Python. For loops are a strong tool for going through sequences and doing tasks repeatedly. Keep practicing with various examples and look into more complex uses as you keep learning Python.