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 - FastCounter[{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
Python | Count occurrences of an element in a list
Given a list in Python and a number x, count number of occurrences of x in the given list.
Examples:
Method 1 [Simple approach]
We keep a counter that keeps on increasing if the required element is found in the list.
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# Python code to count the number of occurrences
def countX[lst, x]:
count = 0
for ele in lst:
if [ele == x]:
count = count + 1
return count
# Driver Code
lst = [8, 6, 8, 10, 8, 20, 10, 8, 8]
x = 8
print['{} has occurred {} times'.format[x, countX[lst, x]]]
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Method 2 [Using count[]]
The idea is to use list method count[] to count number of occurrences.
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# Python code to count the number of occurrences
def countX[lst, x]:
return lst.count[x]
# Driver Code
lst = [8, 6, 8, 10, 8, 20, 10, 8, 8]
x = 8
print['{} has occurred {} times'.format[x, countX[lst, x]]]
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Method 2 [Using Counter[]]
Counter method returns a dictionary with occurrences of all elements as a key-value pair, where key is the element and value is the number of times that element has occurred.
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from collections import Counter
# declaring the list
l = [1, 1, 2, 2, 3, 3, 4, 4, 5, 5]
# driver program
x = 3
d = Counter[l]
print['{} has occurred {} times'.format[x, d[x]]]
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Python List count[]
In this tutorial, we will learn about the Python List count[] method with the help of examples.
The count[] method returns the number of times the specified element appears in the list.
Example
# create a list numbers = [2, 3, 5, 2, 11, 2, 7]Count Occurrences of Element in Python List
Python is well known for its easy syntax, fast implementation, and, most importantly, large support of multiple data structures. Lists are one of those data structures in python which helps to store large amounts of sequential data in a single variable. As huge data is stored under the same variable, it is sometimes quite difficult to manually identify whether the given element is present in the lists, and if yes, how many times. Therefore, in this article, we will study the various ways to count the number of occurrences in the list in python. To recall the concepts of python lists in detail, visit our article “3 Ways to Convert List to Tuple”.