Lists Flashcards
List are:
- 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.
List examples:
my_list = [1,2,3,4]
my_list2 = [‘STRING’,100,23.3]
Cancatinate 2 list
mylist = [‘one’,’two’,’three’]
another_list = [‘apple’,’pie’,’cherry’]
mylist + another_list
Combine two list
mylist = [‘one’,’two’,’three’]
another_list = [‘apple’,’pie’,’cherry’]
mynewlist = mylist + another_list
Change the first string in this list to “One for all’
new_list = [‘one’, ‘two’, ‘three’, ‘four’, ‘five’]
new_list[0] = ‘One for all’
would change it to
new_list = [‘One for all’, ‘two’, ‘three’, ‘four’, ‘five’]
Add an element to the end of a list:
new_list.
new_list.append(‘six’)
new_list = [‘One for all’, ‘two’, ‘three’, ‘four’, ‘five’, ‘six’]
NOTE:This affects the list in place
Remove the last element from a list:
Done using pop
new_list.pop()
new_list = [‘One for all’, ‘two’, ‘three’, ‘four’, ‘five’, ‘six’]
Remove an element from the 3 position
new_list = [‘One for all’, ‘two’, ‘three’, ‘four’, ‘five’, ‘six’]
new_list.pop(3)
new_list = [‘One for all’, ‘two’, ‘three’, ‘five’, ‘six’]
Sort list
new_list = [‘a’, ‘e’, ‘x’, ‘b’, ‘c’]
num_list = [4,1,8,3]
Call the sort method
new_list.sort()
NOTE:This sorts the list in place
Reassign this list but first Sort list
new_list = [‘a’, ‘e’, ‘x’, ‘b’, ‘c’]
num_list = [4,1,8,3]
new_list.sort()
my_sorted_list = new_list
Reverse this list
new_list = [‘a’, ‘e’, ‘x’, ‘b’, ‘c’]
num_list = [4,1,8,3]
- Call the reverse method
- num_list.reverse()
[3,8,1,4]
- new_list.reverse()
[‘c’, ‘b’, ‘e’, ‘a’]
How do I index a nested list? For example if I want to grab 2 from [1,1,[1,2]]?
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.
If lst=[0,1,2] what is the result of lst.pop()
2
Lists can have multiple object types.
True
If lst=[‘a’,’b’,’c’] What is the result of lst[1:]?
[‘b’,’c’]
Are list mutable?
- Yes, Python lists are mutable
- which means you can modify their content (add, remove, or change elements) after creation.
*
What are the immutable data types in Python?
- Strings
- Tuples
- Numbers (integers, floats)
What are the things inside a list called?
Each item is called an Element
Insert an element into a list
- 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’]
~~~
What are the 2 things need to Insert an element into a list?
- 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’]
~~~
How do remove an element from a list?
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
How do remove the last item from a list for later use?
-
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
~~~
How do remove an item from anywhere in list for later use?
-
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
~~~
What is the difference between append() and insert()?
- **appened() **will add an item to the end of a list
- insert() will add an element anywhere in a list
If you use remove(), how many times will it try to remove an item?
- 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.
Remove an item from a list using the value?
-
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
What is sort()?
- **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.
How do you sort, a sort() list in reverse-alphabetical order?
- 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']
How do you sort a list temporarily?
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’]
~~~
What is the difference between sort() and sorted()?
- sort() is a method, meaning it is attahced to the variable
- sort() is permanent change to a list
~~~
cars = [‘bmw’, ‘audi’, ‘toyota’, ‘subaru’]
cars.sort()
print(cars)
[‘audi’, ‘bmw’, ‘subaru’, ‘toyota’]
~~~ - 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']
Copy a list
- 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']
