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Lesson 10

Lesson 10 of 34

List processing

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Code Example

# Example 1
fruits = ["apple", "banana"]
fruits.append("cherry")

# Example 2
numbers = [1, 2, 3]
numbers.append(4)

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A list is like a backpack where you can keep many different items together.
If you want to add something new to the end of your list, you use the append() helper.
Just tell Python which list you are using, then add the new item inside the parentheses.
For example, fruits.append("cherry") puts a cherry at the very end of your fruit list.

Code Example

# Example 1
colors = ["red", "blue"]
more_colors = ["green", "yellow"]
colors.extend(more_colors)

# Example 2
points = [10, 20]
points.extend([30, 40])

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Sometimes you have two different lists and you want to join them together into one big list.
Python has a helper called extend() that lets you pour one list into another.
It doesn't just add one item; it adds every single item from the second list to the end of the first one.
It's like taking two boxes of toys and dumping the smaller box into the bigger one to keep them all together.

Code Example

# Example 1
names = ["Alice", "Charlie"]
names.insert(1, "Bob")  # Puts "Bob" at index 1

# Example 2
queue = [2, 3, 4]
queue.insert(0, 1)      # Puts 1 at the very start

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While append() always goes to the end, insert() lets you pick any spot in your list.
You just need to tell Python two things: the "spot number" and the item you want to put there.
Remember that Python starts counting its spots at 0, so the first spot is actually number 0!
It's like cutting in line—everyone else simply moves over to make room for the new arrival.

Code Example

# Example 1
pets = ["cat", "dog", "bird"]
pets.remove("dog")

# Example 2
scores = [10, 50, 100]
scores.remove(50)

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If you have something in your list that you don't want anymore, you can use remove().
You just need to put the name of the item you want to get rid of inside the parentheses.
Python will look through your list, find that specific item, and take it out for you.
It's like using an eraser to rub out one specific word from a sentence you wrote.

Code Example

# Example 1
letters = ["a", "b", "c"]
last_item = letters.pop()  # Removes "c"

# Example 2
tasks = ["clean", "cook", "sleep"]
first_task = tasks.pop(0)  # Removes "clean"

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The pop() helper is like a "grabber" that takes an item out of your list so you can use it.
If you leave the parentheses empty, Python will automatically grab the very last item in the list.
You can also give it a spot number, like 0, to grab a specific item from that position instead.
Once an item is "popped," it is gone from the list, but you can save it into a variable to use later!

Code Example

# Example 1
prices = [5.0, 1.0, 3.5]
prices.sort()

# Example 2
kids = ["Zane", "Abby", "Mark"]
kids.sort()

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The pop() helper is like a "grabber" that takes an item out of your list so you can use it.
If you leave the parentheses empty, Python will automatically grab the very last item in the list.
You can also give it a spot number, like 0, to grab a specific item from that position instead.
Once an item is "popped," it is gone from the list, but you can save it into a variable to use later!

Code Example

# Example 1
countdown = [1, 2, 3]
countdown.reverse()  # Becomes [3, 2, 1]

# Example 2
words = ["world", "hello"]
words.reverse()      # Becomes ["hello", "world"]

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The pop() helper is like a "grabber" that takes an item out of your list so you can use it.
If you leave the parentheses empty, Python will automatically grab the very last item in the list.
You can also give it a spot number, like 0, to grab a specific item from that position instead.
Once an item is "popped," it is gone from the list, but you can save it into a variable to use later!

Code Example

# Example 1
players = ["Sam", "Jan", "Kit"]
total = len(players)  # total is 3

# Example 2
items = [10, 20, 30, 40, 50]
count = len(items)    # count is 5

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The pop() helper is like a "grabber" that takes an item out of your list so you can use it.
If you leave the parentheses empty, Python will automatically grab the very last item in the list.
You can also give it a spot number, like 0, to grab a specific item from that position instead.
Once an item is "popped," it is gone from the list, but you can save it into a variable to use later!

Code Example

# Example 1: Everyone finished the race
finished = [True, True, True]
result = all(finished)  # result is True
print(result)

# Example 2: One person forgot their shoes
has_shoes = [True, False, True]
result = all(has_shoes) # result is False
print(result)

# Example 3: Checking if all numbers are non-zero
numbers = [1, 5, 10]
result = all(numbers)   # result is True
print(result)

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The pop() helper is like a "grabber" that takes an item out of your list so you can use it.
If you leave the parentheses empty, Python will automatically grab the very last item in the list.
You can also give it a spot number, like 0, to grab a specific item from that position instead.
Once an item is "popped," it is gone from the list, but you can save it into a variable to use later!

Code Example

# Example 1: Someone found the hidden key
found_key = [False, True, False]
result = any(found_key) # result is True
print(result)

# Example 2: Nobody is awake
is_awake = [False, False, False]
result = any(is_awake)  # result is False
print(result)

# Example 3: At least one person has a snack
has_snack = [False, False, True]
result = any(has_snack) # result is True
print(result)

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The pop() helper is like a "grabber" that takes an item out of your list so you can use it.
If you leave the parentheses empty, Python will automatically grab the very last item in the list.
You can also give it a spot number, like 0, to grab a specific item from that position instead.
Once an item is "popped," it is gone from the list, but you can save it into a variable to use later!

Code Example

# Check if all numbers are greater than 2
numbers = [3, 5, 10]
result = all(n > 2 for n in numbers)
print(result)
)

# Check if all words have at least 3 letters
words = ["cat", "dog", "bear"]
result = all(len(w) >= 3 for w in words)
print(result)  # This will be True

# Check if all words have at least 3 letters
users = [{"name": "David","active": True},
{"name": "Mike","active": True}]
result = all(user["active"] for user in users)
print(result)

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The pop() helper is like a "grabber" that takes an item out of your list so you can use it.
If you leave the parentheses empty, Python will automatically grab the very last item in the list.
You can also give it a spot number, like 0, to grab a specific item from that position instead.
Once an item is "popped," it is gone from the list, but you can save it into a variable to use later!

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List processing

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# Example 1: Everyone finished the race finished = [True, True, True] result = all(finished) # result is True print(result) # Example 2: One person forgot their shoes has_shoes = [True, False, True] result = all(has_shoes) # result is False print(result) # Example 3: Checking if all numbers are non-zero numbers = [1, 5, 10] result = all(numbers) # result is True print(result)

# Example 1: Someone found the hidden key found_key = [False, True, False] result = any(found_key) # result is True print(result) # Example 2: Nobody is awake is_awake = [False, False, False] result = any(is_awake) # result is False print(result) # Example 3: At least one person has a snack has_snack = [False, False, True] result = any(has_snack) # result is True print(result)

# Check if all numbers are greater than 2 numbers = [3, 5, 10] result = all(n > 2 for n in numbers) print(result) ) # Check if all words have at least 3 letters words = ["cat", "dog", "bear"] result = all(len(w) >= 3 for w in words) print(result) # This will be True # Check if all words have at least 3 letters users = [{"name": "David","active": True}, {"name": "Mike","active": True}] result = all(user["active"] for user in users) print(result)