Find minimum k records from tuple list in Python

When it is required to find the minimum k records from a list of tuples, it can be done using the sorted() method and lambda function.

The sorted() method is used to sort the elements of a list. Anonymous function is a function which is defined without a name.

In general, functions in Python are defined using def keyword, but anonymous function is defined with the help of lambda keyword. It takes a single expression, but can take any number of arguments. It uses the expression and returns the result of it.

A list can be used to store heterogeneous values (i.e data of any data type like integer, floating point, strings, and so on).

A list of tuple basically contains tuples enclosed in a list.

Below is a demonstration of the same ?

Example

my_list = [(67, 'Will'), (34, 'Mark'), (99, 'Dev'), (2, 'Paul')]

print("The list is:")
print(my_list)
K = 3
print("The value of 'K' has been initialized")

my_result = sorted(my_list, key=lambda x: x[1])[:K]

print("The lowest " + str(K) + " records are:")
print(my_result)

Output

The list is:
[(67, 'Will'), (34, 'Mark'), (99, 'Dev'), (2, 'Paul')]
The value of 'K' has been initialized
The lowest 3 records are:
[(99, 'Dev'), (34, 'Mark'), (2, 'Paul')]

Finding Minimum k Records by Numeric Value

You can also find minimum k records based on numeric values (first element of tuple) ?

my_list = [(67, 'Will'), (34, 'Mark'), (99, 'Dev'), (2, 'Paul')]

print("The list is:")
print(my_list)
K = 2
print("Finding lowest", K, "records by numeric value")

my_result = sorted(my_list, key=lambda x: x[0])[:K]

print("The lowest " + str(K) + " records by number are:")
print(my_result)

The list is:
[(67, 'Will'), (34, 'Mark'), (99, 'Dev'), (2, 'Paul')]
Finding lowest 2 records by numeric value
The lowest 2 records by number are:
[(2, 'Paul'), (34, 'Mark')]

How It Works

• A list of tuples is defined, and displayed on the console.
• The value of K is initialized.
• The sorted() method is used to sort the list of tuples, based on the lambda function which is defined inside it.
• The lambda function key=lambda x: x[1] sorts by the second element (string), while key=lambda x: x[0] sorts by the first element (number).
• Slicing [:K] returns only the first K elements from the sorted list.
• This result is displayed on the console.

Conclusion

Use sorted() with lambda functions to find minimum k records from tuple lists. Sort by different tuple elements using key=lambda x: x[index] and slice with [:K] to get the desired number of minimum records.