Python List (With Examples) - Python lists, how they are created, slicing of a list, adding or removing elements

Python list, how they are created, slicing of a list, adding or removing elements etc.

How to create a list In Python programming, a list is created by placing all the items "elements" inside separated by commas, square brackets []. It can have any number of items and they may have been of different types [string, integer, float etc.]. A list can also have another list as an item. This is called a nested list.

How to create a list?

thislist = ["1", "2", "mango"]
print(thislist)

Output

['1', '2', 'mango']


Access Items/Find Item

 
# list with mixed data types
lst= [1, "Hello", 9.1]
print(lst[1])

Output:

Hello


A list can also have another list as an item. This is called a nested list.
lst = ["mango", [1, 4, 6], ['a']]
print(lst[1])

Output:

[1, 4, 6]

Negative Indexing

Beginning from the end -1 refers to the last items -2 refers to the second last item etc.

lst = ["banana", "sugar", "mango"]
print(lst[-1])

Output:

mango

Basic List Operations
Lists respond to the * and + operators much like strings, they mean repetition and concatenation here too, except that the result is a new list, not a string.

Python Expression Result Description
for x in [1, 2, 3, 4]: print x, 1 2 3 4 Iteration
[1, 2, 3] + [4, 5, 6] [1, 2, 3, 4, 5, 6] Concatenation
['Hi!'] * 5 ['Hi!', 'Hi!', 'Hi!', 'Hi!', 'Hi!'] Repetition
4 in [1, 2, 3, 4] True Membership
len([1, 2, 3 ,4]) 4 Length

What is slicing in python?

The slice() function returns a slice object. A slice object is used to slice strings, lists, tuple etc. You can specify where to start the slicing, and where to end. You can also specify the step, which allows you to e.g. slice only every other item.

In Python List, there are multiple ways to print the whole list with all the elements, but to print a specific range of elements from the list, we use Slice Operation. Slice operation is performed on Lists with the use of a colon(:).

a = ("a", "b", "c", "d", "e", "f", "g", "h", "i")

b = slice(4, 6)

print(a[b])

Output

('e', 'f')

What are tuples in python?

In Python, tuples are written with round brackets. A tuple is a collection that is ordered and unchangeable.

my_tuple = ("apple", "cherry", "banana")
print(my_tuple)

Output

('apple', 'cherry', 'banana')

How to Access Tuple Items

So, you can access tuple items by referring to the index number.

my_tuple = ("apple", "cherry", "banana","mango")
print(my_tuple[2])

Output

banana

How to delete or remove elements from a list in python?

So, you can delete one or more items from a list using the keyword del. It can even delete the list entirely.

# Deleting list items
my_list = ['a', 'b', 'c', 'd', 'e', 'f', 'g']

# delete one item
del my_list[2]

print(my_list)

# delete multiple items
del my_list[1:5]

print(my_list)

# delete entire list
del my_list

# Error: List not defined
print(my_list)

Output

['a', 'b', 'd', 'e', 'f', 'g']
['a', 'g']

List methods in python

Method       Description

index()        Returns the index of the first element with the specified value
insert()        Adds an element at the specified position
pop()          Removes the element at the specified position
remove()    Removes the item with the specified value
reverse()     Reverses the order of the list
sort()          Sorts the list
append()    Adds an element at the end of the list
clear()         Removes all the elements from the list
copy()         Returns a copy of the list
count()       Returns the number of elements with the specified value
extend()     Add the elements of a list, to the end of the current list


The list() Constructor

Use the list() constructor to make a new list.

mylist = list(("apple", "mango", "cherry","banana"))
print(mylist)

Output

['apple', 'mango', 'cherry', 'banana']

Join, or concatenate, two or more lists in Python. One of the easiest ways is by using the + operator.

mylist1 = ["a", "b" , "c"]
mylist2 = [1, 2, 3]

mylist3 = mylist1 + mylist2
print(mylist3)

Output

['a', 'b', 'c', 1, 2, 3]

Another way Append mylist2 into mylist1

mylist1 = ["a", "b" , "c"]
mylist2 = [1, 2, 3]

for x in mylist2:
  mylist1.append(x)

print(mylist1)

Output

['a', 'b', 'c', 1, 2, 3]

Use the extend() method to add mylist2 at the end of mylist1

mylist1 = ["a", "b" , "c","d"]
mylist2 = [1, 2, 3]

mylist1.extend(mylist2)
print(mylist1)

Output

['a', 'b', 'c', 'd', 1, 2, 3]

Copy a List

Use the built-in List method copy().

my_list = ["apple", "mango", "cherry","banana"]
mylist = my_list.copy()
print(mylist)

Output

['apple', 'mango', 'cherry', 'banana']

The clear() method empties the list

mylist = ["apple", "mango", "cherry", "banana"]
mylist.clear()
print(mylist)

Output

[]


Remove Item

There are many methods to remove() items from a list

mylist = ["apple", "mango", "cherry", "banana"]
mylist.remove("mango")
print(mylist)

output

['apple', 'cherry', 'banana']

pop() method removes the specified index

mylist = ["apple", "mango", "cherry", "banana"]
mylist.pop()
print(mylist)

Output

['apple', 'mango', 'cherry']

mylist = ["apple", "mango", "cherry", "banana"]
mylist.pop(2)
print(mylist)

Output

['apple', 'mango', 'banana']

Change Item Value

To change the value of a defined item, refer to the index number

Change the third item

mylist = ["apple", "mango", "cherry", "banana"]
mylist[2] = "pen"

print(mylist)

Output

['apple', 'mango', 'pen', 'banana']

Creating a list with multiple distinct or duplicate elements

A list may contain duplicate values with their distinct positions, multiple distinct or duplicate values can be passed as a sequence at the time of list creation.

# Creating a List with  
# the use of Numbers 
# (Having duplicate values) 
List = [1, 2, 4, 4, 3, 3, 3, 6, 5] 
print("\nList with the use of Numbers: ") 
print(List) 
  
# Creating a List with  
# mixed type of values 
# (Having numbers and strings) 
List = [1, 2, 'minifycode', 4, 'For', 6, 'apple'] 
print("\nList with the use of Mixed Values: ") 
print(List) 

Output

List with the use of Numbers: 
[1, 2, 4, 4, 3, 3, 3, 6, 5]

List with the use of Mixed Values: 
[1, 2, 'minifycode', 4, 'For', 6, 'apple']

2020-09-14