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How to Add a Loop in Python?

Published in Python Loops 3 mins read

To add a loop in Python, you typically use a for loop, which iterates over a sequence. Here's how to create one based on the provided reference:

Steps to Create a For Loop in Python

According to Coursera's guide on for loops, here's how to create a loop:

  1. Start with `for`: Tell Python you're starting a loop by beginning your statement with the keyword for.
  2. Add an iterator variable: This variable will hold the current item during each loop iteration. This is also referred to as the loop variable.
  3. Use the `in` keyword: Follow the iterator variable with the keyword in.
  4. Specify the iterable and a colon: Provide the sequence (like a list, tuple, string, or range) that the loop will iterate through, followed by a colon (`:`).
  5. Add the loop statements: Write the code you want to execute repeatedly within an indented block below the `for` statement.

Example:

my_list = ["apple", "banana", "cherry"]

for fruit in my_list:
    print(fruit)

In this example:

  • for fruit in my_list:: This line initializes the for loop. fruit is the iterator variable, and my_list is the iterable.
  • print(fruit): This line is part of the loop's indented block. It will print the current fruit during each iteration.

Understanding the Components

Here's a breakdown of why each component is important:

  • for: This keyword signals Python that a loop is being initiated.
  • iterator variable: This variable temporarily holds the value of each item in the sequence as the loop proceeds. You can name it anything appropriate (e.g., i, item, or fruit).
  • in: This keyword connects the iterator variable with the iterable object it'll be getting values from.
  • iterable: The iterable can be a collection of data that can be looped through (e.g., lists, strings, ranges, etc.)
  • Colon (:): Marks the end of the for statement.
  • Indented Block: The code inside the loop is distinguished by indentation.

Practical Insights

  • Looping Through Lists: As shown in the example, for loops are commonly used to iterate through lists of items.

  • Looping Through Ranges: Use range() to loop through a sequence of numbers, such as:

     for i in range(5):
        print(i)

    This will output the numbers 0, 1, 2, 3, and 4.

  • Looping Through Strings: Strings are also iterable, allowing you to loop through each character:

my_string = "Python"
for char in my_string:
    print(char)

Alternative Loop (While Loop)

While the for loop is commonly used for iterating over a sequence, Python also has a while loop, which is helpful when you need to loop based on a condition rather than a set sequence. This is an alternative looping method but was not mentioned in the references provided.