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Python

Lists

List Operations

List Creation

# empty list
empty_list = []

# list of integers
int_list = [1, 2, 3]

# list of strings
str_list = ["a", "b", "c"]

# list of mixed data types
mixed_list = [1, "a", 2, "b", 3, "c"]

List Access

# access first element
first_element = mixed_list[0]

# access last element
last_element = mixed_list[-1]

# access elements from index 1 to 3
sub_list = mixed_list[1:4]

# access elements from index 1 to end
sub_list = mixed_list[1:]

# access elements from start to index 3
sub_list = mixed_list[:4]

# access elements from index 1 to 3 with step 2
sub_list = mixed_list[1:4:2]

# access elements from index 1 to end with step 2
sub_list = mixed_list[1::2]

# access elements from start to index 3 with step 2
sub_list = mixed_list[:4:2]

# access elements from start to end with step 2
sub_list = mixed_list[::2]

List Update

# update first element
mixed_list[0] = 4

# update last element
mixed_list[-1] = "d"

# update elements from index 1 to 3
mixed_list[1:4] = [5, "e", 6]

# update elements from index 1 to end
mixed_list[1:] = [5, "e", 6]

# update elements from start to index 3
mixed_list[:4] = [5, "e", 6]

List Delete

# delete first element
del mixed_list[0]

# delete last element
del mixed_list[-1]

# delete elements from index 1 to 3
del mixed_list[1:4]

...

# delete entire list
del mixed_list

List Methods

# append element to end of list
mixed_list.append(4)

# insert element at index 1
mixed_list.insert(1, 5)

# remove first occurence of element
mixed_list.remove(5)

# remove element at index 1
mixed_list.pop(1)

# remove last element
mixed_list.pop()

# reverse list
mixed_list.reverse()

# sort list
mixed_list.sort()

# clear list
mixed_list.clear()

# copy list
mixed_list.copy()

List Functions

# get length of list
len(mixed_list)

# get maximum element
max(mixed_list)

# get minimum element
min(mixed_list)

# get sum of elements
sum(mixed_list)

# get index of first occurence of element
mixed_list.index(5)

# count occurences of element
mixed_list.count(5)

# check if element exists in list
5 in mixed_list

# check if element does not exist in list
5 not in mixed_list

List Comprehension

# create list of squares of numbers from 1 to 10
squares = [x**2 for x in range(1, 11)]

# create list of even numbers from 1 to 10
even_numbers = [x for x in range(1, 11) if x % 2 == 0]

# create list of tuples of numbers from 1 to 10
# where first element is number and second element is square of number
number_squares = [(x, x**2) for x in range(1, 11)]

List Sorting

list = [1,4,2,3,5 ]
list.sort(key=None, reverse=False)

output: [1, 2, 3, 4, 5]

list = [1,4,2,3,5 ]
list.sort(key=None, reverse=True)

output: [5, 4, 3, 2, 1]

List Reversing

list = [1,4,2,3,5 ]
list.reverse()

output: [5, 3, 2, 4, 1]