Learn The First for Loop

Prerequisites

Definition

Loop is a series of instructions that continuously repeats until a specific condition is met. Loops are essential for automating repetitive tasks and efficiently processing data.

Using loops you can iterate over sequences like lists, strings, or numerical ranges, they allow to process large amounts of data with minimal code.

for item in sequence:
    # Perform some operation

item is a variable that takes the value of each element in the sequence one at a time;
sequence is the data you are iterating through, such as a list, string, or range;
for statement block is executed for every item in the sequence.

Imagine you have a string variable and want to print each letter of it in a column. Since a string is a sequence of letters, you can use a loop to achieve this.


              1234567
            
word = 'iteration'
letters = []

# Adding every letter in the word to the list
for letter in word:
    letters.append(letter)
    print(letters)

The word variable holds the string 'iteration'.
The for loop iterates over each character in the string.
Each character is appended to the letters list in each iteration.
After the loop, letters contains all the characters from 'iteration' as individual elements.

Make sure to name the item variable meaningfully. For example, if you iterate through a list called people, the appropriate variable name should be person.

Task

Swipe to start coding

You are a traveler who wants to create a travel list. You have a list of countries and need to add them to your travel list.

Iterate through the countries list using a for loop.
Update travel_list so that it contains only the countries from countries.

Solution

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Section 1. Chapter 1

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