Python Projects for Beginners a ten-Week Bootcamp Approach to Python Programming

Loops and Lists

You can use both the for and while loops to iterate over the items within a list.

Using For Loops

When iterating over a list with a for loop, the syntax looks like when we used the range function previously; however, this time we use a temporary variable, the in keyword, and the name of the list. For each iteration, the temporary variable is assigned the item’s value. Let’s try it out:

# using a for loop to print all items in a list sports = [ "Baseball", "Hockey", "Football", "Basketball" ] for sport in sports: print(sport)

Go ahead and run that cell. Here we can see that this cell will output each item within the list. During the first iteration, the temporary variable “sport” is assigned “Baseball,” and once it prints it out, it moves on to the next item.

Using While Loops

While loops are always used for conditional looping. One great use case for a while loop with lists is removing an item. There are so many uses, this is just one of them:

# using the while loop to remove a certain value names = [ "Bob", "Jack", "Rob", "Bob", "Robert" ] while "Bob" in names:
names.remove("Bob") # removes all instances of 'Bob'
print(names)

Go ahead and run that cell. The output will be our names list without “Bob” in the list. We used the combination of the while loop with a conditional to check for our “Bob” value in the list and then continued to remove it until our condition was no longer true.

THURSDAY EXERCISES

1. 
   Remove Duplicates: remove all duplicates from the list below. hint: Use the
   

.count() method. the output should be [‘Bob’, ‘Kenny’, ‘Amanda’]
>>> names = ['Bob', 'Kenny', 'Amanda', 'Bob', 'Kenny']

2. 
   User Input: Use a while loop to continually ask the user to input a word, until they type “quit”. once they type a word in, add it to a list. once they quit the loop, use a for loop to output all items within the list.
   

today was important so that we could understand how to work with lists, whether it be a conditional statement or a loop. there are many methods out there that lists can use; we’ll go over more of them throughout the rest of this book.