What Does the cmp Function Do in Python Object-Oriented Programming

The cmp() function

The cmp(x,y) function compares the values of two arguments x and y −

cmp(x, y)

The return value is −

A negative number if x is less than y.

Zero if x is equal to y.

A positive number if x is greater than y.

The built-in cmp() function will typically return only the values -1, 0, or 1. However, there are other places that expect functions with the same calling sequence, and those functions may return other values. It is best to observe only the sign of the result.

>>> cmp(2,8)
-1
>>> cmp(6,6)
0
>>> cmp(4,1)
1
>>> cmp('stackexchange', 'stackoverflow')
-1

The method cmp() compares elements of two lists.

Syntax

cmp(list1, list2)

If elements are of the same type, perform the compare and return the result. If elements are different types, check to see if they are numbers.

If numbers, perform numeric coercion if necessary and compare.

If either element is a number, then the other element is "larger" (numbers are "smallest").

Otherwise, types are sorted alphabetically by name.

If we reached the end of one of the lists, the longer list is "larger." If we exhaust both lists and share the same data, the result is a tie, meaning that 0 is returned.

Example

The following example shows the usage of cmp() method.

list1, list2 = [456, 'xyz'], [789, 'abc']
print cmp(list1, list2)
print cmp(list2, list1)
list3 = list2 + [896];
print cmp(list2, list3)

Output

When we run above program, it produces following result −

-1
1
-1