Lists

Question 1

List are:

Answer 1

• A list is a collection of items in a particular order
• Ordered sequences that can hold a variety of object types.
• [] Brackets and commas to separate objects in list [1,2,3,4,5]
• List support indexing and slicing
• List can be nested and also have a variety of useful methods that ce called off of them.

Question 2

List examples:

Answer 2

my_list = [1,2,3,4]

my_list2 = [‘STRING’,100,23.3]

Question 3

Cancatinate 2 list

mylist = [‘one’,’two’,’three’]

another_list = [‘apple’,’pie’,’cherry’]

Answer 3

mylist + another_list

Question 4

Combine two list

mylist = [‘one’,’two’,’three’]

another_list = [‘apple’,’pie’,’cherry’]

Answer 4

mynewlist = mylist + another_list

Question 5

Change the first string in this list to “One for all’

new_list = [‘one’, ‘two’, ‘three’, ‘four’, ‘five’]

Answer 5

new_list[0] = ‘One for all’

would change it to

new_list = [‘One for all’, ‘two’, ‘three’, ‘four’, ‘five’]

Question 6

Add an element to the end of a list:

Answer 6

new_list.

new_list.append(‘six’)

new_list = [‘One for all’, ‘two’, ‘three’, ‘four’, ‘five’, ‘six’]

NOTE:This affects the list in place

Question 7

Remove the last element from a list:

Answer 7

Done using pop

new_list.pop()

new_list = [‘One for all’, ‘two’, ‘three’, ‘four’, ‘five’, ‘six’]

Question 8

Remove an element from the 3 position

new_list = [‘One for all’, ‘two’, ‘three’, ‘four’, ‘five’, ‘six’]

Answer 8

new_list.pop(3)

new_list = [‘One for all’, ‘two’, ‘three’, ‘five’, ‘six’]

Question 9

Sort list

new_list = [‘a’, ‘e’, ‘x’, ‘b’, ‘c’]

num_list = [4,1,8,3]

Answer 9

Call the sort method

new_list.sort()

NOTE:This sorts the list in place

Question 10

Reassign this list but first Sort list

new_list = [‘a’, ‘e’, ‘x’, ‘b’, ‘c’]

num_list = [4,1,8,3]

Answer 10

new_list.sort()

my_sorted_list = new_list

Question 11

Reverse this list

new_list = [‘a’, ‘e’, ‘x’, ‘b’, ‘c’]

num_list = [4,1,8,3]

Answer 11

• Call the reverse method
• num_list.reverse()

[3,8,1,4]

• new_list.reverse()

[‘c’, ‘b’, ‘e’, ‘a’]

Question 12

How do I index a nested list? For example if I want to grab 2 from [1,1,[1,2]]?

Answer 12

You would just add another set of brackets for indexing the nested list, for example:

my_list[2][1]

NOTE: List follow the same numbering sequence as strings.

Question 13

If lst=[0,1,2] what is the result of lst.pop()

Answer 13

2

Question 14

Lists can have multiple object types.

Answer 14

True

Question 15

If lst=[‘a’,’b’,’c’] What is the result of lst[1:]?

Answer 15

[‘b’,’c’]

Question 16

Are list mutable?

Answer 16

• Yes, Python lists are mutable
• which means you can modify their content (add, remove, or change elements) after creation.
  *

Question 17

What are the immutable data types in Python?

Answer 17

• Strings
• Tuples
• Numbers (integers, floats)

Question 18

What are the things inside a list called?

Answer 18

Each item is called an Element

Question 19

Insert an element into a list

Answer 19

• You can add a new element at any position in your list by using the insert() method.
• You do this by specifying the index of the new element and the value of the new item:

motorcycles = ['honda', 'yamaha', 'suzuki']

motorcycles.insert(0, 'ducati')
print(motorcycles)
['ducati', 'honda', 'yamaha', 'suzuki']

Question 20

What are the 2 things need to Insert an element into a list?

Answer 20

• Index where it is going
• New element

motorcycle.insert(3, "harley davidson")
print(motorcycle)
['suzuki', 'yamaha', 'kawasiki', 'harley davidson', 'honda']
motorcycle.insert(0, "triumph")
print(motorcycle)
['triumph', 'suzuki', 'yamaha', 'kawasiki', 'harley davidson', 'honda']

Question 21

How do remove an element from a list?

Answer 21

Delete an element permanently a list

• **del **Statement (This is not a method)

del motorcycle[2]

motorcycle = ['triumph', 'suzuki', 'yamaha', 'kawasiki', 'harley davidson', 'honda']

print(motorcycle)
['triumph', 'suzuki', 'yamaha', 'kawasiki', 'harley davidson', 'honda']
del motorcycle[2]
print(motorcycle)
['triumph', 'suzuki', 'kawasiki', 'harley davidson', 'honda']

• ‘yamaha’ is now missing

Question 22

How do remove the last item from a list for later use?

Answer 22

• pop() method

motorcycle = ['triumph', 'suzuki', 'yamaha', 'kawasiki', 'harley davidson', 'honda']
print(motorcycle)
['triumph', 'suzuki', 'yamaha', 'kawasiki', 'harley davidson', 'honda']
popped_motorcycle = motorcycle.pop()
print(f"The last motorcyle I owneed was a {popped_motorcycle.title()}.")
The last motorcyle I owneed was a Honda.
print(popped_motorcycle)
honda

Question 23

How do remove an item from anywhere in list for later use?

Answer 23

• pop() method

# Remove an element for later use in a list from any where in the list
motorcycle = ['triumph', 'suzuki', 'yamaha', 'kawasiki', 'harley davidson', 'honda']
print(motorcycle)
['triumph', 'suzuki', 'yamaha', 'kawasiki', 'harley davidson', 'honda']

popped_motorcycle = motorcycle.pop(3)
print(f"The last motorcyle I owneed was a {popped_motorcycle.title()}.")
The last motorcyle I owneed was a Kawasiki.
print(popped_motorcycle)
kawasiki

Question 24

What is the difference between append() and insert()?

Answer 24

• **appened() **will add an item to the end of a list
• insert() will add an element anywhere in a list

Question 25

If you use **remove()**, how many times will it try to remove an item?

Answer 25

* The **remove() **method deletes only the first occurrence of the value you specify. * If there’s a possibility the value appears more than once in the list, you’ll need to use a loop to make sure all occurrences of the value are removed.

Question 26

Remove an item from a list using the value?

Answer 26

* **remove()** method ``` # Remove an element by vaule from a list motorcycle = ['triumph', 'suzuki', 'yamaha', 'kawasiki', 'harley davidson', 'honda'] print(motorcycle) motorcycle.remove('yamaha') ['triumph', 'suzuki', 'yamaha', 'kawasiki', 'harley davidson', 'honda'] # print(f"The last motorcyle I owneed was a {popped_motorcycle.title()}.") print(motorcycle) ['triumph', 'suzuki', 'kawasiki', 'harley davidson', 'honda'] ``` * 'yamaha' is now missing

Question 27

What is sort()?

Answer 27

* **sort() **is a method * The **sort()** method changes the order of the list permanently. * You can also sort this list in reverse-alphabetical order by passing the argument reverse=True to the sort() method.

Question 28

How do you sort, a **sort()** list in reverse-alphabetical order?

Answer 28

* You can also sort this list in reverse-alphabetical order by passing the argument **reverse=True** to the **sort()** method. ``` cars = ['bmw', 'audi', 'toyota', 'subaru'] cars.sort() print(cars) ['audi', 'bmw', 'subaru', 'toyota'] cars.sort(reverse=True) print(cars) ['toyota', 'subaru', 'bmw', 'audi'] ```

Question 29

How do you sort a list temporarily?

Answer 29

# print("\nHere is the sorted list:") * **sorted() ** function * Lets you display your list in a particular order, but doesn’t affect the actual order of the list. ``` cars = ['bmw', 'audi', 'toyota', 'subaru'] print(cars) ['bmw', 'audi', 'toyota', 'subaru'] print(sorted(cars)) ['audi', 'bmw', 'subaru', 'toyota'] # print("\nHere is the original list again:") print(cars) ['bmw', 'audi', 'toyota', 'subaru'] ```

Question 30

What is the difference between **sort()** and **sorted()**?

Answer 30

1. **sort()** is a method, meaning it is attahced to the variable 2. sort() is permanent change to a list ``` cars = ['bmw', 'audi', 'toyota', 'subaru'] cars.sort() print(cars) ['audi', 'bmw', 'subaru', 'toyota'] ``` 1. **sorted()** is a Function ``` # Original list cars = ['bmw', 'audi', 'toyota', 'subaru'] print(sorted(cars)) # Here is the sorted list: ['audi', 'bmw', 'subaru', 'toyota'] # Here is the original list again: ['bmw', 'audi', 'toyota', 'subaru'] ```

Question 31

Copy a list

Answer 31

* First, we make a list of the foods we like called my_foods. * Then we make a new list called friend_foods. * We make a copy of my_foods by asking for a slice of my_foods without specifying any indices ❶, and assign the copy to friend_foods. * When we print each list, we see that they both contain the same foods: ``` my_foods = ['pizza', 'falafel', 'carrot cake'] ❶ friend_foods = my_foods[:] print("My favorite foods are:") print(my_foods) My favorite foods are: ['pizza', 'falafel', 'carrot cake'] print("\nMy friend's favorite foods are:") print(friend_foods) My friend's favorite foods are: ['pizza', 'falafel', 'carrot cake'] ```