In this article, we will discuss how we get the number of elements in a list.
Example:
Input: [1,2,3,4,5]
Output: 5
Explanation: No of elements in the list are 5Input: [1.2 ,4.5, 2.2]
Output: 3
Explanation: No of elements in the list are 3Input: [“apple”, “banana”, “mangoe”]
Output: 3
Explanation: No of elements in the list are 3
Before getting the Number of Elements in the Python List, we have to create an empty List and store some items into the list.
There are three methods to get the number of elements in the list, i.e.:
- Using Python len( ) function
- Using for loop
- Using operator length_hint function
Using Len() function to Get the Number of Elements
We can use the len( ) function to return the number of elements present in the list.
Python3
# declare list of itemselem_list = [1, 2, 3, 4]# printing the listprint(elem_list)# using the len() which return the number# of elements in the listprint("No of elements in list are:", len(elem_list)) |
Output:
[1, 2, 3, 4] No of elements in list are: 4
Time Complexity: O(1)
Auxiliary Space: O(1)
Using for loop Get the Number of Elements
We can declare a counter variable to count the number of elements in the list using a for loop and print the counter after the loop in Python gets terminated.
Python3
# declare list of itemsitem_list = [1, 2, 3, 4]# declare a counter variablecount = 0# iterate on items using for-loop# and keep increasing the value of countfor i in item_list: # increment the value of count count = count+1# print the list elementsprint(item_list)print("No of elements in the list are:", count) |
Output:
[1, 2, 3, 4] No of elements in the list are: 4
Time Complexity: O(n)
Auxiliary Space: O(1)
Using length_hint Get the Number of Elements in a List
Python3
from operator import length_hintl = [1, 2, 3, 4]print(length_hint(l)) |
Output:
4
Time Complexity: O(1)
Auxiliary Space: O(1)
Using Sum Get the Number of Elements in a List
Python
# declare list of itemselem_list = [1, 2, 3, 4]# printing the listprint(elem_list)# using the sum() which return the number# of elements in the listprint("No of elements in list are:", sum(1 for i in elem_list)) |
Output:
4
Time Complexity: O(n), where n is the number of elements in the list
Auxiliary Space: O(1)
Using Numpy Library
Note: Install numpy module using command “pip install numpy”
Python3
import numpy as np # declare list of itemselem_list = [1, 2, 3, 4] # printing the listprint(elem_list) # using the numpy library# to return the number of elements in the listprint("No of elements in list are:", np.size(elem_list)) |
Output:
[1, 2, 3, 4]
No of elements in list are: 4
Time Complexity: O(n), where n is the number of elements in the list
Auxiliary Space: O(1)
