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Python – Value list lengths

  • Last Updated : 29 Dec, 2019

Many times, while dealing with containers in any language we come across lists of tuples in different forms, tuples in themselves can have sometimes more than native datatypes and can have list as their attributes. This article talks about the length of list as tuple attribute. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using list comprehension + len()
This particular problem can be solved using list comprehension combined with the len function in which we use len function to find the len of list as a tuple attribute and list comprehension to iterate through the list.




# Python3 code to demonstrate
# Value list lengths
# using list comprehension + len()
  
# initializing list
test_list = [('key1', [3, 4, 5]), ('key2', [1, 4, 2]), ('key3', [9, 3])]
  
# printing original list
print("The original list : " + str(test_list))
  
# using list comprehension + len()
# Value list lengths
res = [(key, len(lst)) for key, lst in test_list]
  
# print result
print("The list tuple attribute length is : " + str(res))
Output :
The original list : [('key1', [3, 4, 5]), ('key2', [1, 4, 2]), ('key3', [9, 3])]
The list tuple attribute length is : [('key1', 3), ('key2', 3), ('key3', 2)]

 

Method #2 : Using map + lambda + len()
The above problem can also be solved using the map function to extend the logic to the whole list and len function can perform the similar task as the above method.






# Python3 code to demonstrate
# Value list lengths
# using map() + lambda + len()
  
# initializing list
test_list = [('key1', [3, 4, 5]), ('key2', [1, 4, 2]), ('key3', [9, 3])]
  
# printing original list
print("The original list : " + str(test_list))
  
# using map() + lambda + len()
# Value list lengths
res = list(map(lambda x: (x[0], len(x[1])), test_list))
  
# print result
print("The list tuple attribute length is : " + str(res))
Output :
The original list : [('key1', [3, 4, 5]), ('key2', [1, 4, 2]), ('key3', [9, 3])]
The list tuple attribute length is : [('key1', 3), ('key2', 3), ('key3', 2)]

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