Saturday, February 1, 2020

Lists in Python

Lists In Python


Lists


The List is one of the most widely utilized collection in Python programs. The list is more like an array. The difference between an array and a list is that a list in Python may have different types of elements but an array has all the elements of the same type. List are both mutable and a sequence data type that permits them to be indexed. The list can have different types of objects, including other list-objects.

We can declare a list like,

l=[12,5,21,3.1,'python','c',0.399, 300]

The members of the list are contained within [] brackets(square).

A list can be accessed by indices.

List in python


Basic operations on a list


The general operation those can be performed on lists are print, iterate, append, pop, remove, reverse, count, sort, etc)

Iterating list


We can iterate them with for loop,

list=[23,'Python',4.78,'programming','a','b',456,True,11,-45]
for x in list:
  print(x)

Output:
23
Python
4.78
programming
a
b
456
True
11
-45

Accessing list with index position 


We can randomly access a list's elements by using its indices like

list=[23,'Python',4.78,'programming','a','b',456,True,11,-45]
print('Element at index 3 is ',list[3])
print('')
print('Elements in range of index 2 to 7 are ',list[2:7])


Output:
Element at index 3 is  programming

Elements in range of index 2 to 7 are  [4.78, 'programming', 'a', 'b', 456]

We can use negative index also like(-1 is last index,-2 is second last and so-on)

list=[23,'Python',4.78,'programming','a','b',456,True,11,-45]
print('|Elements [-6:-2]|',list[-6:-2])

Output:
|Elements [-6:-2]| ['a', 'b', 456, True]

append() method


We can append a list as lists are dynamic data structures

list=[23,'Python',4.78,'programming','a','b',456,True,11,-45]
list.append('dyanmic')
print(list)

Output:
[23, 'Python', 4.78, 'programming', 'a', 'b', 456, True, 11, -45, 'dyanmic']

pop() method


We can remove the last element from list using the pop() function

list=[23,'Python',4.78,'programming','a','b',456,True,11,-45]
list.pop()
print(list)

Output:
[23, 'Python', 4.78, 'programming', 'a', 'b', 456, True, 11]


remove() method


We can remove any element by its value from the list

list=[23,'Python',4.78,'programming','a','b',456,True,11,-45]
list.remove('b')
list.remove(4.78)
print(list)

Output:
[23, 'Python', 'programming', 'a', 456, True, 11, -45]


reverse() method


We can also reverse a list by the reverse() method.

list=[23,'Python',4.78,'programming','a','b',456,True,11,-45]
list.reverse()
print('Reversed list is ',list)

Output:
Reversed list is  [-45, 11, True, 456, 'b', 'a', 'programming', 4.78, 'Python', 23]

count() method


This method can be used to count the number occurrence of an Element in a list.

list=[23,'Python',4.78,'programming','a','a',456,True,11,-45]
count=list.count('a')
print('Total elements are ',count)

Output:
Total elements are  2

sort() method


A list can be sorted using the sort() method.

list=[23,25,12,19,110,11,-45]
list.sort()
print('sorted list',list)

Output:
sorted list [-45, 11, 12, 19, 23, 25, 110]