Python – List Words Frequency in String

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0 0 3 minutes read

Given a List of Words, Map frequency of each to occurrence in String.

Input : test_str = 'zambiatek is best for Lazyroar and best for CS', count_list = ['best', 'zambiatek', 'computer'] 
Output : [2, 1, 0] 
Explanation : best has 2 occ., zambiatek 1 and computer is not present in string.
Input : test_str = 'zambiatek is best for Lazyroar and best for CS', count_list = ['better', 'gfg', 'computer'] 
Output : [0, 0, 0] 
Explanation : No word from list present in string.

Method #1 : Using defaultdict() + loop + list comprehension

In this, we compute words frequency using loop + defaultdict() and then use list comprehension to get all the counts corresponding to list of words.

Python3




# Python3 code to demonstrate working of
# Divide String into Equal K chunks
# Using list comprehension
from collections import defaultdict
 
# Initializing strings
test_str = 'zambiatek is best for Lazyroar and best for CS'
 
# Printing original string
print("The original string is : " + str(test_str))
 
# Initializing count_list
count_list = ['best', 'zambiatek', 'computer', 'better', 'for', 'and']
 
# Computing frequency
res = defaultdict(int)
 
for sub in test_str.split():
    res[sub] += 1
 
# Assigning to list words
res = [res[sub] for sub in count_list]
 
# Printing result
print("The list words frequency : " + str(res))
 



















Output






The original string is : zambiatek is best for Lazyroar and best for CS
The list words frequency : [2, 1, 0, 0, 2, 1]




Time Complexity: O(n)
Auxiliary Space: O(n), where n is the length of the list.


Method #2 : Using Counter() + list comprehension


In this, Counter() is used to perform the task of computing frequency, post that, list comprehension is used to assign a frequency to list words.






Python3


















 






 




 



























# Python3 code to demonstrate working of 


# Divide String into Equal K chunks


# Using list comprehension


from collections import Counter


 


# initializing strings


test_str = 'zambiatek is best for Lazyroar and best for CS'


 


# printing original string


print("The original string is : " + str(test_str))


 


# initializing count_list 


count_list = ['best', 'zambiatek', 'computer', 'better', 'for', 'and']


 


# computing frequency using Counter()


res = Counter(test_str.split())


     


# assigning to list words


res = [res[sub] for sub in count_list]


 


# printing result 


print("The list words frequency : " + str(res)) 










































Output


The original string is : zambiatek is best for Lazyroar and best for CS
The list words frequency : [2, 1, 0, 0, 2, 1]




Time complexity: O(N) since using a loop
Auxiliary Space: O(1)


Method #3 : Using count() method


Approach


    

  1. Split the string test_str which results in a list(x)
    2. 

  2. Initiate a for loop to traverse the list of strings.
    3. 

  3. Now append the occurrence of each string in x to the output list.
    4. 

  4. Display output list.
    5. 





Python3


















 






 




 



























# Python3 code to demonstrate working of


# Divide String into Equal K chunks


 


# Initializing strings


test_str = 'zambiatek is best for Lazyroar and best for CS'


 


# Printing original string


print("The original string is : " + str(test_str))


x=test_str.split()


 


# Iitializing count_list


count_list = ['best', 'zambiatek', 'computer', 'better', 'for', 'and']


 


# Cmputing frequency


res=[]


 


for i in count_list:


    res.append(x.count(i))


 


# Pinting result


print("The list words frequency : " + str(res))










































Output


The original string is : zambiatek is best for Lazyroar and best for CS
The list words frequency : [2, 1, 0, 0, 2, 1]




Time Complexity : O(M*N) M – length of x N – length of count_list
Auxiliary Space : O(N) N – length of output list


Method #4: Using dictionary comprehension




In this method, we can use a dictionary comprehension to count the frequency of each word in the given string. The keys of the dictionary will be the words from the count_list, and the values will be the frequency of each word in the given string. 






Python3


















 






 




 



























# Python3 code to demonstrate working of


# Divide String into Equal K chunks


 


 


# initializing strings


test_str = 'zambiatek is best for Lazyroar and best for CS'


 


# printing original string


print("The original string is : " + str(test_str))


 


# initializing count_list


count_list = ['best', 'zambiatek', 'computer', 'better', 'for', 'and']


 


# computing frequency using dictionary comprehension


res = {i: test_str.split().count(i) for i in count_list}


 


# printing result


print("The list words frequency : " + str([res[i] for i in count_list]))










































Output


The original string is : zambiatek is best for Lazyroar and best for CS
The list words frequency : [2, 1, 0, 0, 2, 1]




Time complexity: O(N), where n is the length of the given string.
Auxiliary space: O(K), where k is the number of words in the count_list.






			
		


				

			

				

						
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