Array/List Methods in Python

1. append(x):

Adds an element to the end of the list

syntax: list.append(element)

l = [7, 6, 7, 5, 4, 9]

l.append(5)
print(l)

output: [7, 6, 7, 5, 4, 9, 5]

2. insert(i, x):

Insert an element at a given index.

syntax: list.insert(index, element)

l = [7, 6, 7, 5, 4, 9, 5]

l.insert(1, 3)
print(l)

output: [7, 3, 6, 7, 5, 4, 9, 5]

3. remove(x):

Removes the first occurrence of the given element.

syntax: list.remove(element)

l = [7, 3, 6, 7, 5, 4, 9, 5]

l.remove(5)
print(l)

output: [7, 3, 6, 7, 4, 9, 5]

4. pop(i):

Removes the element from the given index. If no index is given, it removes the last element from the list.

syntax: list.pop(index)

l = [7, 3, 6, 7, 4, 9, 5]

l.pop(2)
print(l)

l.pop()
print(l)

output: [7, 3, 7, 4, 9, 5], [7, 3, 7, 4, 9]

5. index(x, s, e):

Returns the list's first index of a given element. Start and end parameters are optional and specify the index to start the search from and, end to. If only one parameter other than the element is given, it defaults to start. If element is not found in the list, it returns a ValueError.

syntax: list.index(element, start (optional), end (optional))

l = [7, 3, 7, 4, 9, 7]

x = l.index(7)
print(x)

y = l.index(7, 2)
print(y)

z = l.index(7, 3, 6)
print(z)

p = l.index(5)
print(p)

output: 0 , 2 , 5 , ValueError

6. count(x):

Counts the number of times an element appears in the list

syntax: list.count(element)

l = [7, 3, 7, 4, 9]

x = l.count(7)
print(x)

output: 2

7. sort(*, key = , reverse = True/False):

Sorts the list in ascending (by-default), descending, alphabetical (by-default), reverse-alphabetical, or according to a user-given order.

syntax: list.sort(*, key = , reverse = True/False(Default))

l1 = [7, 3, 7, 4, 9]

l1.sort()
print(l1)

l1.sort(reverse = True)
print(l1)

l2 = ['bb', 'a', 'dddd', 'ccc']

l2.sort()
print(l2)

l2.sort(reverse=True)
print(l2)

l2.sort(key = len)
print(l2)

l2.sort(key = len, reverse = True)
print(l2)

output: [3, 4, 7, 7, 9], [9, 7, 7, 4, 3], ['a', 'bb', 'ccc', 'dddd'], ['dddd', 'ccc', 'bb', 'a'], ['a', 'bb', 'ccc', 'dddd'], ['dddd', 'ccc', 'bb', 'a']

8. reverse():

Reverses the elements of the given list.

syntax: list.reverse()

l = [7, 3, 7, 4, 9]

l.reverse()
print(l)

output: [9, 4, 7, 3, 7]

9. copy():

Returns a copy of the given list.

syntax: list2 = list1.copy()

l1 = [9, 4, 7, 3, 7]

l2 = l1.copy()
print(l1)

output: [9, 4, 7, 3, 7]

10. extend(list):

Adds elements of the second list to the end of the first list.

syntax: list1.extend(list2)

l1 = [9, 4, 7, 3, 7]
l2 = ['bb', 'a', 'dddd', 'ccc']

l1.extend(l2)
print(l1)

output: [9, 4, 7, 3, 7, 'bb', 'a', 'dddd', 'ccc']

11. clear():

Removes all the elements of the given list.

syntax: list.clear()

l1 = [9, 4, 7, 3, 7, 'bb', 'a', 'dddd', 'ccc']

l1.clear()
print(l1)

output: []

REFERENCES

• Python Documentation