Python – Minimum in each record value list

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 min of list as tuple attribute. Let’s discuss certain ways in which this task can be performed. 

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

Python3

# Python3 code to demonstrate
# Record Value list Minimum
# using list comprehension + min()

# 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 + min()
# Record Value list Minimum
res = [(key, min(lst)) for key, lst in test_list]

# print result
print("The list tuple attribute minimum is : " + str(res))

Output : 

The original list : [('key1', [3, 4, 5]), ('key2', [1, 4, 2]), ('key3', [9, 3])]
The list tuple attribute minimum is : [('key1', 3), ('key2', 1), ('key3', 3)]

Time complexity: O(M^N) as the number of combinations generated is M choose N.
Auxiliary space: O(M^N) as the size of the resultant list is also M choose N.

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

Python3

# Python3 code to demonstrate
# Record Value list Minimum
# using map() + lambda + min()

# 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 + min()
# Record Value list Minimum
res = list(map(lambda x: (x[0], min(x[1])), test_list))

# print result
print("The list tuple attribute minimum is : " + str(res))

Output : 

The original list : [('key1', [3, 4, 5]), ('key2', [1, 4, 2]), ('key3', [9, 3])]
The list tuple attribute minimum is : [('key1', 3), ('key2', 1), ('key3', 3)]

Time complexity: O(M^N) as the number of combinations generated is M choose N.
Auxiliary space: O(M^N) as the size of the resultant list is also M choose N.

Method #3 : Using reduce()

Python3

# Using reduce

from functools import reduce

# Initializing list
test_list = [('key1', [3, 4, 5]), ('key2', [1, 4, 2]), ('key3', [9, 3])]

# Finding minimum in each sublist using reduce
result = [(key, reduce(lambda x, y: x if x<y else y, lst)) for key, lst in test_list]

# Printing the final result
print("The list tuple attribute minimum is:", result)

Output

The list tuple attribute minimum is: [('key1', 3), ('key2', 1), ('key3', 3)]

Time complexity: O(n^2)
Space complexity: O(n)

Explanation:
In this approach, we use the reduce function from the functools library to find the minimum in each sublist. We iterate through the list of tuples and use the reduce function to find the minimum of each sublist. Finally, we store the result in a new list of tuples and print the result.

Method 4: Use a loop to iterate through the list of tuples and finding the minimum value for each tuple’s value list.

Python3

# Python3 code to demonstrate
# Record Value list Minimum
# using for loop

# 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 for loop
# Record Value list Minimum
res = []
for key, lst in test_list:
    min_val = min(lst)
    res.append((key, min_val))

# print result
print("The list tuple attribute minimum is : " + str(res))

Output

The original list : [('key1', [3, 4, 5]), ('key2', [1, 4, 2]), ('key3', [9, 3])]
The list tuple attribute minimum is : [('key1', 3), ('key2', 1), ('key3', 3)]

Time Complexity: O(n * m), where n is the length of the list and m is the length of the longest value list.
Auxiliary Space: O(n), where n is the length of the list.

Method 5: Uses a dictionary comprehension

This method uses a dictionary comprehension to create a dictionary where the keys are the first elements of the tuples and the values are the minimum values of the second elements of the tuples. Then, it converts the dictionary to a list of tuples.

Python3

# Python3 code to demonstrate
# Record Value list Minimum
# using dictionary comprehension

# 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 dictionary comprehension
# Record Value list Minimum
res_dict = {key: min(lst) for key, lst in test_list}
res = list(res_dict.items())

# print result
print("The list tuple attribute minimum is : " + str(res))

Output

The original list : [('key1', [3, 4, 5]), ('key2', [1, 4, 2]), ('key3', [9, 3])]
The list tuple attribute minimum is : [('key1', 3), ('key2', 1), ('key3', 3)]

Time complexity: O(n)
Auxiliary space: O(n)

Method #6: Using itertools.chain() and min()

• Import itertools module.
• Use itertools.chain() function to flatten the list of lists into a single list.
• Use min() function to find the minimum value in the flattened list.
• Repeat the above steps for each list of tuples in the given list and store the minimum value in a list.
• Create a new list of tuples with keys from the original list and minimum values from the list created in step 4.

Python3

import itertools

# 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 itertools.chain() and min()
# Record Value list Minimum
res = []
for key, lst in test_list:
    min_val = min(itertools.chain(*[lst]))
    res.append((key, min_val))

# print result
print("The list tuple attribute minimum is : " + str(res))

Output

The original list : [('key1', [3, 4, 5]), ('key2', [1, 4, 2]), ('key3', [9, 3])]
The list tuple attribute minimum is : [('key1', 3), ('key2', 1), ('key3', 3)]

Time complexity: O(nm) where n is the number of tuples in the list and m is the length of the longest list in the tuples.
Auxiliary space: O(nm) to store the flattened list.