List

Common List Operations

Method name	Description
x in s	True if element x is in sequence s, False otherwise
x not in s	True if element x is not in sequence s, False otherwise
s1 + s2	Concatenates two sequences s1 and s2
s * n , n * s	n copies of sequence s concatenated
s[i]	ith element in sequence s.
len(s)	Length of sequences, i.e. the number of elements ins`.
min(s)	Smallest element in sequence s.
max(s)	Largest element in sequence s.
sum(s)	Sum of all numbers in sequence s.
for loop	Traverses elements from left to right in a for loop.

List examples using functions

>>> list1 = [2, 3, 4, 1, 32]
>>> 2 in list1
# True

>>> 33 not in list1
# True

>>> len(list1) # find the number of elements in the list
# 5

>>> max(list1) # find the largest element in the list
# 32

>>> min(list1) # find the smallest element in the list
# 1

>>> sum(list1) # sum of elements in the list
# 42

List slicing

>>> list = [11,33,44,66,788,1]
>>> list[0:5] # this will return list starting from index 0 to index 4
# [11,33,44,66,788]

>>> list[:3] 
# [11,33,44]

>>> list[2:] 
# [44,66,788,1]

+ and * operators in list

>>> list1 = [11, 33]
>>> list2 = [1, 9]
>>> list3 = list1 + list2
>>> list3
# [11, 33, 1, 9]

>>> list4 = [1, 2, 3, 4]
>>> list5 = list4 * 3
>>> list5
# [1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4]

in or not in operator

# in
>>> list1 = [11, 22, 44, 16, 77, 98]
>>> 22 in list1
# True

# not in
>>> 22 not in list1
# False

Traversing list using for loop

>>> list = [1,2,3,4,5]
>>> for i in list:
... print(i, end=" ")
# 1 2 3 4 5

List Comprehension

>>> list1 = [ x for x in range(10) ]
>>> list1
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]


>>> list2 = [ x + 1 for x in range(10) ]
>>> list2
# [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

>>> list3 = [ x for x in range(10) if x % 2 == 0 ]
>>> list3
# [0, 2, 4, 6, 8]

>>> list4 = [ x *2 for x in range(10) if x % 2 == 0 ]
# [0, 4, 8, 12, 16]

Commonly used list methods with return type

Method name	Description
append(x:object):None	Adds an element x to the end of the list and returns None.
count(x:object):int	Returns the number of times element x appears in the list.
extend(l:list):None	Appends all the elements in l to the list and returns None.
index(x: object):int	Returns the index of the first occurrence of element x in the list
insert(index: int, x: object):None	Inserts an element x at a given index. Note that the first element in the list has index 0 and returns None.
remove(x:object):None	Removes the first occurrence of element x from the list and returns None
reverse():None	Reverse the list and returns None
sort(): None	Sorts the elements in the list in ascending order and returns None.
pop(i): object	Removes the element at the given position and returns it. The parameter i is optional. If it is not specified, pop() removes and returns the last element in the list.

>>> list1 = [2, 3, 4, 1, 32, 4]
>>> list1.append(19)
>>> list1
# [2, 3, 4, 1, 32, 4, 19]

>>> list1.count(4) # Return the count for number 4
# 2

>>> list2 = [99, 54]
>>> list1.extend(list2)
>>> list1
# [2, 3, 4, 1, 32, 4, 19, 99, 54]

>>> list1.index(4) # Return the index of number 4
# 2

>>> list1.insert(1, 25) # Insert 25 at position index 1
>>> list1
# [2, 25, 3, 4, 1, 32, 4, 19, 99, 54]

>>>
>>> list1 = [2, 25, 3, 4, 1, 32, 4, 19, 99, 54]
>>> list1.pop(2)
# 3

>>> list1
# [2, 25, 4, 1, 32, 4, 19, 99, 54]

>>> list1.pop()
# 54

>>> list1
# [2, 25, 4, 1, 32, 4, 19, 99]

>>> list1.remove(32) # Remove number 32
>>> list1
# [2, 25, 4, 1, 4, 19, 99]

>>> list1.reverse() # Reverse the list
>>> list1
# [99, 19, 4, 1, 4, 25, 2]

>>> list1.sort() # Sort the list
>>> list1
# [1, 2, 4, 4, 19, 25, 99]