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Python Lists
*Lists are created using square brackets:
*List items are ordered, changeable, and allow duplicate values.
List items are indexed, the first item has index [0], the second item has index [1] etc.
*If you add new items to a list, the new items will be placed at the end of the list
mylist = ["apple", "banana", "cherry"]
Changeable
The list is changeable, meaning that we can change, add, and remove items in a list after it has been created.
len, datatype
*A list can contain different data types:
list1 = ["abc", 34, True, 40, "male"]
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Access Items
Note: The first item has index 0.
thislist = ["apple", "banana", "cherry"]
print(thislist[1])
*negative indexing also possible
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*Range of index
thislist = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]
print(thislist[2:5])
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Python - Change List Items
To change the value of a specific item, refer to the index number:
thislist = ["apple", "banana", "cherry"]
thislist[1] = "blackcurrant"
print(thislist)
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Change a Range of Item Values
replace item with new one
EXAMPLE
Change the values "banana" and "cherry" with the values "blackcurrant" and "watermelon":
thislist = ["apple", "banana", "cherry", "orange", "kiwi", "mango"]
thislist[1:3] = ["blackcurrant", "watermelon"]
print(thislist)
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Insert Items
To insert a new list item, without replacing any of the existing values, we can use the insert() method.
The insert() method inserts an item at the specified index:
Example
Insert "watermelon" as the third item:
thislist = ["apple", "banana", "cherry"]
thislist.insert(2, "watermelon")
print(thislist)
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Python - Add List Items
To add an item to the end of the list, use the append() method:
thislist = ["apple", "banana", "cherry"]
thislist.append("orange")
print(thislist)
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Extend List
To append elements from another list to the current list, use the extend() method.
extend() method
Example
Add the elements of tropical to thislist:
thislist = ["apple", "banana", "cherry"]
tropical = ["mango", "pineapple", "papaya"]
thislist.extend(tropical)
print(thislist)
Add Any Iterable
The extend() method does not have to append lists, you can add any iterable object (tuples, sets, dictionaries etc.).
Example
Add elements of a tuple to a list:
thislist = ["apple", "banana", "cherry"]
thistuple = ("kiwi", "orange")
thislist.extend(thistuple)
print(thislist)
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Remove Specified Item
thislist = ["apple", "banana", "cherry"]
thislist.remove("banana")
print(thislist)
Note: if there are multiple same item it will remove first one
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Remove Specified Index
EXAMPLE- remove first item
thislist = ["apple", "banana", "cherry"]
thislist.pop(1)
print(thislist)
Note:If you do not specify the index, the pop() method removes the last item.
syntax- thislist.pop()
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The del keyword also removes the specified index:
EXAMPLE
thislist = ["apple", "banana", "cherry"]
del thislist[0]
print(thislist)
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Delete the entire list:
thislist = ["apple", "banana", "cherry"]
del thislist
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Clear the List
The clear() method empties the list.
EXAMPLE
thislist = ["apple", "banana", "cherry"]
thislist.clear()
print(thislist)
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Sort List Alphanumerically
thislist = ["orange", "mango", "kiwi", "pineapple", "banana"]
thislist.sort()
print(thislist)
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Python - Copy Lists
Example
Make a copy of a list with the copy() method:
thislist = ["apple", "banana", "cherry"]
mylist = thislist.copy()
print(mylist)
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Python - Join Lists
list1 = ["a", "b", "c"]
list2 = [1, 2, 3]
list3 = list1 + list2
print(list3)
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Python List index() Method
fruits = ['apple', 'banana', 'cherry']
x = fruits.index("cherry")
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