Python For Loop: Basics, Examples, and Problem Solving

In this lecture, we’ll learn about the Python For Loop. After Learning Python While Loop We’ll start with the basics and gradually explore more advanced topics. The “for” loop is a powerful tool for repeating tasks, and we’ll show you how to use it effectively. Through easy-to-understand examples and hands-on exercises, you’ll become confident in using the “for” loop to solve various problems.

Python For Loop:

A For Loop is a control flow statement that iterates over a sequence (such as a list, tuple, string, or range) and executes a block of code for each element in the sequence. The basic syntax is:

for item in sequence:
 # code to be executed for each item in the sequence

The loop continues until all items in the sequence have been processed.

Program 1: Counting with a For Loop

# Title: Square Numbers

for i in range(1, 6):

 square = i ** 2

 print(f"Number: {i}, Square: {square}")

Explanation:

• This program uses a for loop to iterate over a range of numbers from 1 to 5 (inclusive).
• Inside the loop, it calculates the square of each number (i ** 2) and prints both the original number and its square.

Conditionals within a Loop:

Similar to a “while” loop, you can use “if” statements inside a “for” loop to introduce conditional logic. This allows you to execute specific code based on conditions during each iteration of the loop.

for item in sequence:

 # code to be executed for each item in the sequence

 if some_condition:

 # code to be executed when some_condition is true

 else:

 # code to be executed when some_condition is false

Counting Using For Loop:

A “for” loop is commonly used for counting, especially when iterating over a range of numbers. For example:

for i in range(1, 6):

 print(i)

This loop will print the numbers 1 through 5.

“in” Operator with For Loop:

The “in” operator is often used with a “for” loop to iterate over the elements of a sequence. It checks if a particular element is present in the sequence and, if true, executes the code inside the loop.

my_list = [1, 2, 3, 4, 5]

for item in my_list:

 print(item)

This loop iterates over each element in the list my_list, printing each item during each iteration.

Program 2: Conditional Filtering with For Loop

# Title: Even Numbers

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

for num in numbers:

 if num % 2 == 0:

 print(f"Even Number: {num}")

Explanation:

• This program initializes a list of numbers.
• The for loop iterates over each number in the list.
• Inside the loop, there’s an “if” statement checking if the number is even (num % 2 == 0).
• If the number is even, it prints a message indicating that it is an even number.

Python For Loop: Problem Examples

Here are 10 problem examples involving for loops, conditionals within a loop, counting using a for loop, and the use of the “in” operator:

1: Use a for loop to print the numbers from 1 to 5.

2: Modify the previous program to skip printing multiples of 3.

3: Develop a program utilizing a for loop to count down from 10 to 1.

4: Employ a for loop to calculate and print the sum of the first 5 even numbers.

5: Create a program with a for loop to check if each character in a given word is a vowel.

6: Print the squares of numbers from 1 to 5 using a for loop.

7: Check whether a given number is prime using a for loop and conditionals.

8: Utilize a for loop and conditionals to print only the odd numbers from a given list of numbers.

9: Count and print the occurrences of a specific character in a given string using a for loop.

10: Verify the presence of a given element in a list using a for loop and the “in” operator.

These exercises encompass various aspects of for loops, conditionals within loops, counting, and the “in” operator, promoting active practice in Python programming.