In this tutorial we are going to learn :

  • What is Python List
  • list () and len () methods
  • Accessing Items
  • List Unpacking

 

 

What is Python List

 
  • A list is a collection that is ordered and changeable.
  • In Python, we use square brackets to create a list.
  • We can store integer, strings, floats, etc. in our lists.

 

Example :

As you can see we can store any type of data in our lists.

list_of_numbers = [1, 2, 3, 4, 5]
list_of_strings = ["James", "John", "Adam"]
matrix = [[1, 2], [3, 5], [7, 2]]   # list inside of list
my_list = [1, "James", 2.1, 7]


print(list_of_numbers)
print(list_of_strings)
print(matrix)
print(my_list) 
 
  • We can use  *  for storing the same type of data in our list. 
  • We can use  +  to combine lists.

Example :

number = [1] * 10       # instead of writing 10 times, we use * to do it
my_list = ["a", "b", "c", "d"]

combine = number + my_list

print(combine) 

 

 

 

list() and len() Methods

 
  • We can also use the list() function to create a list.
  • To learn how many items our list has, we use the len() function.

 

Example :

# using list() function 

first_list = list(range(10))    # 0 to 10 but 10 is not included
second_list = list("Hello World")


# using len() function 

numbers_of_item = len(second_list)


# printing
print(first_list)
print(second_list)
print(f"Numbers of item : {numbers_of_item}") 

 

 

 

Accessing Items

 

You can access items by referring to the index number.

Example :

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

# Accessing Items
print(my_list[0])
print(my_list[-1])

# List Slicing 
print(my_list[:])   # Accessing all items
print(my_list[0:])  # Accessing all items
print(my_list[0:3]) # Accessing index 0 to index 3, ,index 3 is not incuded 
print(my_list[:3])  # Accessing index 0 to index 3, index 3 is not included 
print(my_list[1:5]) # Accessing index 1 to index 5, index 5 is not included  




List Unpacking


  • If we have a list with many items we can access some items using the list unpacking method.
  • We use the  *  operator for list unpacking.


Example :

my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9]

first, second, *rest_of = my_list 

print(f" First : {first} \n Second : {second} \n Rest of : {rest_of}")

# Accessing first and last items
first, *rest_of, last = my_list

print(f"\n First item : {first} \n Second item : {last} \n Rest of : {rest_of}") 
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