Learn Loop Control Statements in a while Loop

The break and continue statements are powerful tools for controlling the flow of a while loop:

break: immediately exits the loop when a specific condition is met;
continue: skips the rest of the current iteration and moves to the next one.

Additionally, the pass statement is used as a placeholder and does nothing when executed, which can be useful for incomplete logic or avoiding errors in empty blocks.

Let's use a while loop to search for a specific city in the travel_list. If the city is found, the loop will terminate using break.


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travel_list = ['Monako', 'Luxemburg', 'Liverpool', 'Barcelona', 'Munchen']

# Initialize the index
i = 0

# Search for "Barcelona"
while i < len(travel_list):
    if travel_list[i] == 'Barcelona':
        print('Found Barcelona!')
        break
    print(travel_list[i])
    i += 1

The index i starts at 0, pointing to the first city in the list;
The while loop continues as long as i is less than the length of travel_list;
If the current city is "Barcelona", the message is printed, and the loop exits using break and "Munchen" is never reached by the loop;
If "Barcelona" is not found, the current city is printed, and i is incremented to move to the next city.

Now, let's count how many times "Barcelona" appears in the travel_list, skipping cities that don't match using continue.


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travel_list = ['Monako', 'Barcelona', 'Liverpool', 'Barcelona', 'Munchen', 'Barcelona']

# Initialize variables
i = 0
counter = 0

# Count occurrences of "Barcelona"
while i < len(travel_list):
    if travel_list[i] != 'Barcelona':
        i += 1
        continue
    else:
        counter += 1
    i += 1

print('Total occurrences of Barcelona:', counter)

The index i starts at 0, and counter is set to 0 to track occurrences of 'Barcelona';
The while loop runs as long as i is less than the length of travel_list;
If the current city is not 'Barcelona', the loop skips the remaining code for that iteration using continue and increments i;
For each occurrence of 'Barcelona', counter is incremented, and the loop continues until all cities are checked.

Task

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You are organizing a country database and need to filter out only the countries that start with the letter 'S'. However, to keep the list manageable, you decide to limit the selection to just 3 countries.

Iterate through the countries list using a while loop.
Skip any country that does not start with 'S'.
Add only the first 3 valid countries to the selected list.

Solution

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Section 2. Chapter 4

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