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Higher Order Sort in Python

Built-in sort functions

The sort() function modifies the original list. Consider the below code. 

student_list=[('Aditi',50),('Vaibhav',68),('Akshay',70)]

# To sort in ascending order
student_list.sort()

print("student_list in ascending order = ",student_list)

# To sort in descending order
student_list.sort(reverse=True)

print("student_list in descending order = ",student_list)
Output
student_list in ascending order = [('Aditi',50),('Akshay',70),('Vaibhav',68)]
student_list in descending order = [('Vaibhav',68),('Akshay',70),('Aditi',50)]
The sorted() function returns a new copy of the original list after sorting it.

student_list=[('Aditi',50),('Vaibhav',68),('Akshay',70)]
print("student_list = ",student_list)

print()

sorted_student_list=sorted(student_list)
print("sorted_student_list = ",sorted_student_list)
Output
student_list =  [('Aditi',50),('Vaibhav',68),('Akshay',70)]

sorted_student_list = [('Aditi',50),('Akshay',70),('Vaibhav',68)]

Higher Order Sort

By default, if we sort an object, it gets sorted based on its first property. As we can see in the above examples, student_list contains tuples of student and their marks. On applying the sort function, it gets sorted based on the names since it is the first property in the tuples. But suppose you want to sort the list based on the marks rather than names without changing the original list.
The sort function accepts a keyword argument key that accepts a function that provides the property of the object on the basis of which you want to sort. Consider the below code. 

# func accepts every item of the student_list i.e. each tuple and returns the marks of each tuple.
def func(student):
    return student[1]
    
student_list=[('Aditi',50),('Vaibhav',68),('Akshay',70)]
student_list.sort(key=func)
print(student_list)
Output
[('Aditi', 50), ('Vaibhav', 68), ('Akshay', 70)]