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Learn to Code: Python for Absolute Beginners

Introduction to Loops

Explore the concept of loops in Python to automate repetitive tasks. Learn how for loops iterate over ranges and sequences, understand loop execution through examples, and write programs that generate arithmetic or geometric sequences. Develop foundational skills to manage repetition effectively in coding problems.

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Repetition

The repetition of an instruction or a group of instructions is a commonly encountered phenomenon in programming called a loop. As an example, let’s say we want our program to perform the following tasks:

  • To read a document or data file line by line repeatedly until the end of the file.
  • To draw an image pixel by pixel repeatedly using color values that show it on the screen.
  • To iterate through a collection of variables one by one to process its values.
  • To compute a result by applying a formula to several values.

The for loop

Let’s say we want to display integers from 00 to 44. We can simply display the numbers 00 to 44 one by one using the print() statement. We can also use one variable and print its value repeatedly by changing the value of the variable, as shown below:

Python 3.10.4
# Multiple print statements with help of variable a
a = 0
print(a)
a = 1
print(a)
a = 2
print(a)
a = 3
print(a)
a = 4
print(a)

The code above clearly shows the repetitive use of print(a). The benefit of using a single variable is that we can convert this repetition into a for loop. In Python, we use a for loop to perform a process repeatedly for a ...