How do you count the number of values in a list Python?

Python count

The count[] is a built-in function in Python. It will return the total count of a given element in a list. The count[] function is used to count elements on a list as well as a string.

In this Python tutorial, you will learn:

• Python count
• Python List count[]
• Example 1: List Count
• Example 2: Find the count of elements [Duplicates] in a givenlist

Below are the three solutions:

Fastest is using a for loop and storing it in a Dict.

import time from collections import Counter def countElement[a]: g = {} for i in a: if i in g: g[i] +=1 else: g[i] =1 return g z = [1,1,1,1,2,2,2,2,3,3,4,5,5,234,23,3,12,3,123,12,31,23,13,2,4,23,42,42,34,234,23,42,34,23,423,42,34,23,423,4,234,23,42,34,23,4,23,423,4,23,4] #Solution 1 - Faster st = time.monotonic[] for i in range[1000000]: b = countElement[z] et = time.monotonic[] print[b] print['Simple for loop and storing it in dict - Duration: {}'.format[et - st]] #Solution 2 - Fast st = time.monotonic[] for i in range[1000000]: a = Counter[z] et = time.monotonic[] print [a] print['Using collections.Counter - Duration: {}'.format[et - st]] #Solution 3 - Slow st = time.monotonic[] for i in range[1000000]: g = dict[[[i, z.count[i]] for i in set[z]]] et = time.monotonic[] print[g] print['Using list comprehension - Duration: {}'.format[et - st]]

Result

#Solution 1 - Faster

{1: 4, 2: 5, 3: 4, 4: 6, 5: 2, 234: 3, 23: 10, 12: 2, 123: 1, 31: 1, 13: 1, 42: 5, 34: 4, 423: 3} Simple for loop and storing it in dict - Duration: 12.032000000000153

#Solution 2 - Fast

Counter[{23: 10, 4: 6, 2: 5, 42: 5, 1: 4, 3: 4, 34: 4, 234: 3, 423: 3, 5: 2, 12: 2, 123: 1, 31: 1, 13: 1}] Using collections.Counter - Duration: 15.889999999999418

#Solution 3 - Slow

{1: 4, 2: 5, 3: 4, 4: 6, 5: 2, 34: 4, 423: 3, 234: 3, 42: 5, 12: 2, 13: 1, 23: 10, 123: 1, 31: 1} Using list comprehension - Duration: 33.0

Count elements in a flat list

Suppose we have a list i.e.

# List of strings listOfElems = ['Hello', 'Ok', 'is', 'Ok', 'test', 'this', 'is', 'a', 'test']
To count the elements in this list, we have different ways. Let’s explore them,

Use len[] function to get the size of a list

Python provides a inbuilt function to get the size of a sequence i.e.

len[s]
Arguments:

• s : A sequence like object like, list, string, bytes, tuple etc.

It returns the length of object i.e. count of elements in the object.

Now let’s use this len[] function to get the size of a list i.e.

listOfElems = ['Hello', 'Ok', 'is', 'Ok', 'test', 'this', 'is', 'a', 'test'] # Get size of a list using len[] length = len[listOfElems] print['Number of elements in list : ', length]
Output:
Number of elements in list : 9
How does len[] function works ?

When len[s] function is called, it internally calls the __len__[] function of the passed object s. Default sequential containers like list, tuple & string has implementation of __len__[] function, that returns the count of elements in that sequence.

So, in our case we passed the list object to the len[] function. Which internally called the __len__[] of the list object, to fetch the count of elements in list.

Use list.__len__[] to count elements in a list

We can directly call the __len__[] member function of list to get the size of list i.e.

listOfElems = ['Hello', 'Ok', 'is', 'Ok', 'test', 'this', 'is', 'a', 'test'] # Get size of a list using list.__len__[] length = listOfElems.__len__[] print['Number of elements in list : ', length]
Output:
Number of elements in list : 9
Although we got the size of list using __len__[] function. It is not a recommended way, we should always prefer len[] to get the size of list.

[1] Count the Number of Elements in a Python List that Contains Strings

To start with a simple example, let’s create a list that contains 5 names:

names_list = ['Jeff', 'Ben', 'Maria', 'Sophia', 'Rob'] print[names_list]

Run the syntax above, and you’ll get the following list:

['Jeff', 'Ben', 'Maria', 'Sophia', 'Rob']

You can then use the len[] function in order to count the number of elements in the list:

names_list = ['Jeff', 'Ben', 'Maria', 'Sophia', 'Rob'] print[len[names_list]]

Once you run the code in Python, you’ll get the count of 5.

Let’s extend the list by additional 3 names, and then recount the number of elements:

names_list = ['Jeff', 'Ben', 'Maria', 'Sophia', 'Rob'] names_list.extend[['Laura','Elizabeth','Justin']] print[len[names_list]]

You’ll now get the count of 8.