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Python – Dictionary value lists lengths product
  • Last Updated : 01 Aug, 2020

Given a dictionary with values as lists, compute lengths of each list, and find product of all lengths.

Input : test_dict = {‘Gfg’ : [6, 5, 9, 3], ‘is’ : [1, 3, 4], ‘best’ :[9, 16]}
Output : 24
Explanation : 4 * 3 * 2 = 24. Length of lists are 4, 3, and 2.

Input : test_dict = {‘Gfg’ : [6, 5, 3], ‘is’ : [1, 3, 4], ‘best’ :[9, 16]}
Output : 18
Explanation : 3 * 3 * 2 = 18. Length of lists are 3, 3, and 2.

Method #1 : Using loop + len()

This is one of the ways in which this task can be performed. In this, we iterate for all the values and use len() to get length of all value lists, post which we perform multiplication of whole data.



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# Python3 code to demonstrate working of 
# Dictionary value lists lengths product
# Using loop + len()
  
# initializing dictionary
test_dict = {'Gfg' : [6, 5, 9, 3, 10],
             'is' : [1, 3, 4], 
             'best' :[9, 16]}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# using loop to iterate through all keys 
res = 1
for key in test_dict:
      
    # len() used to get length of each value list
    res = res * len(test_dict[key])    
  
# printing result 
print("The computed product : " + str(res)) 

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Output

The original dictionary is : {'Gfg': [6, 5, 9, 3, 10], 'is': [1, 3, 4], 'best': [9, 16]}
The computed product : 30

Method #2 : Using map() + lambda + reduce() 

The combination of above functions provide one-liner approach to solve this problem. In this, we use map() to get lengths of all lists extending len() to each list, lambda is used to get product and reduce to combine.

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# Python3 code to demonstrate working of 
# Dictionary value lists lengths product
# Using map() + lambda + reduce() 
from functools import reduce
  
# initializing dictionary
test_dict = {'Gfg' : [6, 5, 9, 3, 10],
             'is' : [1, 3, 4], 
             'best' :[9, 16]}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# values() used to get all lists of keys
res = reduce(lambda sub1, sub2: sub1 * sub2, map(len, test_dict.values()))
  
# printing result 
print("The computed product : " + str(res)) 

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Output

The original dictionary is : {'Gfg': [6, 5, 9, 3, 10], 'is': [1, 3, 4], 'best': [9, 16]}
The computed product : 30

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