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Python – Step Frequency of elements in List

  • Last Updated : 01 Mar, 2020

Sometimes, while working with Python, we can have a problem in which we need to compute frequency in list. This is quite common problem and can have usecase in many domains. But we can atimes have problem in which we need incremental count of elements in list. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using loop + defaultdict()
The combination of above functions can be used to perform this task. In this, we just initialize list with a default value and increment its frequency using a loop.




# Python3 code to demonstrate 
# Step Frequency of elements in List
# using loop + defaultdict()
from collections import defaultdict
  
# Initializing loop 
test_list = ['gfg', 'is', 'best', 'gfg', 'is', 'life']
  
# printing original list 
print("The original list is : " + str(test_list))
  
# Step Frequency of elements in List
# using loop + defaultdict()
res_d = defaultdict(int)
res = []
for ele in test_list:
    res_d[ele] += 1
    res.append(res_d[ele])
  
# printing result 
print ("Step frequency of elements is : " + str(res))
Output :
The original list is : ['gfg', 'is', 'best', 'gfg', 'is', 'life']
Step frequency of elements is : [1, 1, 1, 2, 2, 1]

 

Method #2 : Using list comprehension + enumerate()
The combination of above functions can be used to solve this problem. In this we just iterate and store the counter using enumerate().






# Python3 code to demonstrate 
# Step Frequency of elements in List
# using list comprehension + enumerate()
from collections import defaultdict
  
# Initializing loop 
test_list = ['gfg', 'is', 'best', 'gfg', 'is', 'life']
  
# printing original list 
print("The original list is : " + str(test_list))
  
# Step Frequency of elements in List
# using list comprehension + enumerate()
res = [test_list[ : idx + 1].count(ele) for (idx, ele) in enumerate(test_list)]
  
# printing result 
print ("Step frequency of elements is : " + str(res))
Output :
The original list is : ['gfg', 'is', 'best', 'gfg', 'is', 'life']
Step frequency of elements is : [1, 1, 1, 2, 2, 1]

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