Using For Loops in Python (with Examples)

The basic

In Python, a for loop is a type of loop that is used to iterate over a sequence of items, such as a list, a tuple, a dictionary, a set, or a string. A for loop executes a block of code for each item in the sequence until the sequence is exhausted or a break statement is encountered.

Syntax:

for item in sequence:
    # do something with item

Explanation:

• The for keyword initiates the loop.
• item is a variable that represents each item in the sequence for each iteration.
• sequence is the sequence of items to iterate over.
• The colon (:) indicates the start of the code block that will be executed for each iteration.
• The indented block of code is the body of the loop that is executed for each item.

Basic example:

years = [2023, 2024, 2025, 2026, 2027]

for year in years:
    print(f"Year: {year}")

Output:

Year: 2023
Year: 2024
Year: 2025
Year: 2026
Year: 2027

Another example:

text = "Sling Academy"
for letter in text:
    print(letter)

Output:

S
l
i
n
g
 
A
c
a
d
e
m
y

Using a “for” loop with the range() function

When using a for loop with the range() function, you can iterate over a sequence of numbers within a specified range. The range() function generates a sequence of numbers based on the provided start, stop, and step values.

The syntax of the range() function is as follows:

range(start, stop, step)

Where:

• start (optional) specifies the starting value of the range (inclusive). If not provided, it defaults to 0.
• stop specifies the ending value of the range (exclusive). The generated sequence will contain numbers up to, but not including, the stop value.
• step (optional) specifies the increment between each number in the sequence. If not provided, it defaults to 1.

Example:

for num in range(5):
    print(num)

Output:

0
1
2
3
4

This example Iterates over a range of numbers from 1 to 10 (exclusive), incrementing by 2:

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

Output:

1
3
5
7
9

In case you want to iterate over a range of numbers in reverse order, just use a negative step like this:

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

Output:

10
9
8
7
6
5
4
3
2
1

Using a “for” loop with the “break” statement

You can use the break statement to stop a for loop before it has run through all the items.

Example:

fruits = ["apple", "banana", "cherry"]
for x in fruits:
    print(x)
    if x == "banana":
        break

Output:

apple
banana

Using a “for” loop with the “continue” statement

The continue statement stops the current iteration of a for loop and continues with the next one.

Example:

fruits = ["apple", "banana", "cherry", "mango"]
for x in fruits:
    if x == "banana":
        continue
    print(x)

Output:

apple
cherry
mango

Using a “for” loop with the “else” clause

You can use a for loop with the else clause to execute a block of code when the loop is finished.

Example:

for x in range(6):
    print(x)
else:
    print("Finally finished!")

Output:

0
1
2
3
4
5
Finally finished!