Python | Selective value selection in list of tuples

Sometimes, while using list of tuples, we come across a problem in which we have a certain list of keys and we just need the value of those keys from list of tuples. This has a utility in rating or summation of specific entities. Let’s discuss certain ways in which this can be done.

Method #1 : Using dict() + get() + list comprehension
We can perform this particular task by first, converting the list into the dictionary and then employing list comprehension to get the value of specific keys using get function.

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# Python3 code to demonstrate  
# Selective Value selection in list of tuples
# using dict() + get() + list comprehension
  
# initializing list of tuples 
test_list = [('Nikhil', 1), ('Akash', 2), ('Akshat', 3), ('Manjeet', 4)]
  
# initializing selection list 
select_list = ['Nikhil', 'Akshat']
  
# printing original list 
print ("The original list is : " + str(test_list))
  
# printing selection list 
print ("The selection list is : " + str(select_list))
  
# using dict() + get() + list comprehension
# Selective Value selection in list of tuples
temp = dict(test_list)
res = [temp.get(i, 0) for i in select_list]
  
# printing result
print ("The selective values of keys : " + str(res))

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Output :



The original list is : [(‘Nikhil’, 1), (‘Akash’, 2), (‘Akshat’, 3), (‘Manjeet’, 4)]
The selection list is : [‘Nikhil’, ‘Akshat’]
The selective values of keys : [1, 3]

 

Method #2 : Using next() + list comprehension
This particular problem can be solved using the next function which performs the iteration using the iterators and hence more efficient way to achieve a possible solution.

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# Python3 code to demonstrate  
# Selective Value selection in list of tuples
# using next() + list comprehension
  
# initializing list of tuples 
test_list = [('Nikhil', 1), ('Akash', 2), ('Akshat', 3), ('Manjeet', 4)]
  
# initializing selection list 
select_list = ['Nikhil', 'Akshat']
  
# printing original list 
print ("The original list is : " + str(test_list))
  
# printing selection list 
print ("The selection list is : " + str(select_list))
  
# using next() + list comprehension
# Selective Value selection in list of tuples
res = [next((sub[1] for sub in test_list 
       if sub[0] == i), 0) for i in select_list]
  
# printing result
print ("The selective values of keys : " + str(res))

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Output :

The original list is : [(‘Nikhil’, 1), (‘Akash’, 2), (‘Akshat’, 3), (‘Manjeet’, 4)]
The selection list is : [‘Nikhil’, ‘Akshat’]
The selective values of keys : [1, 3]



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