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Python for Loop

Video link: https://youtu.be/yaqMSBr_NCU

In this video, we learned about loops to repeat certain blocks of code, specifically using the for loop.

Programs in the Video

Python Sequences

A sequence is a collection of items in an order. We have already used strings numerous times in our programs. A string is basically a sequence of characters.

# Python sequences
text = "Python"
languages = ['English', 'French', 'German']

The sequence with three items separated by commas and enclosed in square brackets is called a list. We will learn about them in the upcoming tutorials.

Python for loop

The for loop in Python is used to iterate over a sequence, and in each iteration, we can access individual items of that sequence.

The syntax of the for loop in Python is:

for item in sequence:
   statement(s)

Here, the statements inside the for loop are executed for every item in sequence.

Example: Using for Loops

text = "Python"

for character in text:
    print(character)

Output

P
y
t
h
o
n

Here, using a for loop we have accessed individual items of this string one by one.

During the first iteration of the loop, the variable character will be the first letter 'P' and it gets printed to the screen.

The loop continues similarly until we reach the last item in the sequence.

Looping Through a List

We can use the for loop to iterate through each item of this list one by one.

languages = ["English", "French", "German"]

for language in languages:
    print(language)

Output

English
French
German

Python range()

In the previous tutorial, we used while loop to repeat a block of code a certain number of times.

count = 1

while count <= 5:
    print(count)
    count = count + 1

Output

1
2
3
4
5

We can use range() with a for loop to write this program in a much simpler way.

for count in range(1, 6):
    print(count)

Output

1
2
3
4
5

The range() function creates a sequence of numbers from 1 to 5. The last value passed (6 in this case) is exclusive.

Example: Multiplication Table

number = int(input("Enter an integer: "))

for count in range(1, 11):
    product = number * count
    print(number, "*", count, "=", product)

Output

Enter an integer: 9
9 * 1 = 9
9 * 2 = 18
9 * 3 = 27
9 * 4 = 36
9 * 5 = 45
9 * 6 = 54
9 * 7 = 63
9 * 8 = 72
9 * 9 = 81
9 * 10 = 90

Programming Task

Can you create a program to find the sum of numbers from 1 to 100.

The result should be equal to 1 + 2 + 3 + ... + 100.

total = 0

# looping from 1 to 100
for number in range(1, 101):
    total = total + number
print(total)

Output

5050