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video: What is it and Why do we Use it? | Python For loop Tutorial
Syntax:
for item in iterable:
# code block
iterable is a sequence of elements such as a list, tuple, dictionary, set, or string. item is a variable that takes on the value of each element in the sequence, one at a time. The code block is executed once for each element in the sequence.
range() function:
range() function as an iterable in a for loop in Python. The range() function returns a sequence of numbers, starting from 0 by default, and increments by 1 (by default), and ends at a specified number.Here are the common usages:
stop):
range(stop)
0 up to, but not including, stop.range(5) # Output: 0, 1, 2, 3, 4
start, stop):
range(start, stop)
start up to, but not including, stop.range(2, 5) # Output: 2, 3, 4
start, stop, step):
range(start, stop, step)
start up to, but not including, stop, incrementing by step. The step can be positive or negative.range(1, 10, 2) # Output: 1, 3, 5, 7, 9
range(10, 1, -2) # Output: 10, 8, 6, 4, 2
Note: range() produces an immutable sequence type, which is often used in loops. To get a list of numbers, you can convert the range object to a list:
list(range(5)) # Output: [0, 1, 2, 3, 4]
Question: Write a Python program to print the numbers from 1 to 5, using a for loop.
for i in range(6):
print(i)
Question: Write a Python program to print the string “Building the future, one line at a time.” 5 times, using a for loop.
for i in range(5):
print("Building the future, one line at a time.")
Question: Write a python program to calculate the sum of the first N natural numbers using a for loop.
video: Calculate the sum of the first N natural numbers | Python for loop example
Description:
Write a Python program that asks the user to input two numbers, a start and an end value, and calculates the sum of all the numbers in that range (inclusive) using a for loop.
Input:
Output:
Example:
Input:
Enter the start of the range: 1
Enter the end of the range: 5
Output:
The sum of numbers from 1 to 5 is: 15
Requirements:
for loop to iterate through the range.Description:
Write a Python program that asks the user to input two numbers, a start and an end value, and displays all the even numbers between the two values (inclusive) using a for loop.
Input:
Output:
Example:
Input:
Enter the start of the range: 2
Enter the end of the range: 10
Output:
2
4
6
8
10
Requirements:
for loop to iterate through the range.%) operator.Question: Write a Python program to display the even numbers from 2 to 10 and sum of even numbers, inclusive, using a for loop.
sum = 0
for i in range(2,11):
if i%2 == 0:
sum +=i
print(i)
print(f"Sum of even numbers: {sum}")
Description:
Write a Python program that asks the user to input a number and displays its multiplication table up to 10 using a for loop.
Input:
Output:
n x 1 = n
n x 2 = 2n
...
n x 10 = 10n
Example:
Input:
Enter a number: 5
Output:
5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
5 x 4 = 20
5 x 5 = 25
5 x 6 = 30
5 x 7 = 35
5 x 8 = 40
5 x 9 = 45
5 x 10 = 50
Requirements:
for loop to generate and display the multiplication table.collection = ['python', 5, 'd']
for x in collection:
print(x)
list_of_lists = [ [1, 2, 3], [4, 5, 6], [7, 8, 9]]
for list in list_of_lists:
for x in list:
print(x)
for i in range(1, 11):
print(f"Multiplication table of {i}")
for j in range(1, 11):
print('%d * %d = %d' % (i, j, i*j))
In Python, a variable in a for loop is used to iterate over a sequence (like a list, tuple, string, or range) and access each element in that sequence one at a time. This variable is often called the “loop variable” or “iterator variable.”
Understanding the Role of the Variable:
Accessing Elements: The loop variable allows you to access each element in the sequence during each iteration of the loop. This makes it possible to perform operations on each element.
Dynamic Assignment: The loop variable automatically takes the value of the next element in the sequence during each iteration. This saves you from having to manually update the variable’s value.
Readability and Simplicity: Using a loop variable makes the code more readable and easier to understand. You can name the variable in a way that reflects the data it represents, making the code more self-explanatory.
Control Over Iteration: The loop variable gives you control over the loop’s execution. You can use it to control the flow, such as skipping certain elements, breaking out of the loop early, or performing specific actions based on the variable’s value.
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
print(fruit)
In this example, the loop variable fruit takes on the value of each element in the list fruits during each iteration. The output will be:
apple
banana
cherry
The variable fruit is used to access and print each element in the fruits list.
_) is often used as a variable name in a for loop (or any other context) when the value of the variable is not needed.For example, if you want to repeat an action a certain number of times but don’t need to use the loop variable, you can use _:
for _ in range(5):
print("Hello")
Here, _ is used instead of a variable name like i or j because the value is not important. The loop will simply print “Hello” five times without using the loop index. This helps to make the code more readable by signaling to other programmers that the loop variable is not used in the loop’s body.