How To Create A Loop In Python

In this tutorial, we will learn one of the essential programming concepts – creating loops in Python.

Loops are useful for iterating or repeating a series of statements a certain number of times or until a specific condition is met. Python offers two types of loops: for loops and while loops. We’ll go through these two types of loops with examples and demonstrate how to use them effectively in your code.

Step 1: Understanding For Loops in Python

In Python, a for loop is utilized when you want to iterate over a sequence (like a list, tuple, set, or dictionary), where the loop executes the specified block of code for each element in the sequence. Here’s the basic syntax for for loop:

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for item in sequence:
    # Code to be executed

Let’s look at an example of iterating through a list using a for loop.

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numbers_list = [1, 2, 3, 4, 5]
 
for number in numbers_list:
    print(number)

Output:

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5

Step 2: Understanding While Loops in Python

A while loop is utilized when you want to execute a block of code repeatedly until a specified condition is false. The syntax for a while loop is:

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while condition:
    # Code to be executed

Here’s an example of using a while loop to print numbers from 1 to 5.

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

Output:

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5

Step 3: Using the Range Function with For Loops

If you need to create a loop that iterates a specific number of times, you can use the built-in Python function range(). The range() function generates a sequence of numbers, starting from 0 by default, and increments by 1 (also by default). It can take up to 3 arguments:

  • start: The starting number of the sequence (optional, defaults to 0)
  • stop: The last number of the sequence (required)
  • step: The incrementation value (optional, defaults to 1)

Here’s an example of using a for loop with the range() function:

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for i in range(5):
    print(i)

Output:

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Step 4: Using Nested Loops

A nested loop is a loop inside another loop. This can be helpful if you need to iterate through multiple sequences or repeat a block of code for different combinations of values. Here’s an example using nested for loops to create a multiplication table:

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for i in range(1, 11):
    for j in range(1, 11):
        print(i * j, end="\t")
    print()

Output:

1   2   3   4   5   6   7   8   9   10  
2   4   6   8   10  12  14  16  18  20  
3   6   9   12  15  18  21  24  27  30  
4   8   12  16  20  24  28  32  36  40  
5   10  15  20  25  30  35  40  45  50  
6   12  18  24  30  36  42  48  54  60  
7   14  21  28  35  42  49  56  63  70  
8   16  24  32  40  48  56  64  72  80  
9   18  27  36  45  54  63  72  81  90  
10  20  30  40  50  60  70  80  90  100

Full Example Code

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# For loop example
numbers_list = [1, 2, 3, 4, 5]
 
for number in numbers_list:
    print(number)
 
# While loop example
number = 1
 
while number <= 5:
    print(number)
    number += 1
 
# For loop with range
for i in range(5):
    print(i)
 
# Nested for loops example
for i in range(1, 11):
    for j in range(1, 11):
        print(i * j, end="\t")
    print()

Conclusion

In conclusion, loops are essential when it comes to executing a series of statements repeatedly. By understanding how to create and use for loops, while loops, range(), and nested loops in Python, you’ll be able to simplify your code and minimize repetitive tasks.

Remember that Python loop syntax might be a bit different from other programming languages, so make sure you familiarize yourself with Python’s unique syntax.