Python pow() Function

The pow() function in Python returns the value of a number raised to a given power. It can also return the result modulo another number. This makes it very useful in both basic arithmetic and advanced algorithms like cryptography.

Syntax

pow(base, exponent[, modulus])

Parameters:

• base – The number to be raised (required)
• exponent – The power to raise the base to (required)
• modulus – The number to divide the result by and return remainder (optional)

Returns:

• If 2 arguments: base ** exponent
• If 3 arguments: (base ** exponent) % modulus

Example 1: Basic Power Calculation

print(pow(2, 3))

8

Example 2: Power with Negative Exponent

print(pow(2, -2))

0.25

Example 3: Power with Modulus

print(pow(2, 3, 5))

3

This returns (2**3) % 5 = 8 % 5 = 3.

Use Cases

• Quickly raise a number to a power
• Perform modular exponentiation efficiently (especially in large number computations)
• Used in cryptographic algorithms like RSA

Important Notes

• pow(a, b, c) is more efficient than (a ** b) % c
• If modulus is provided, all values must be integers
• For floating-point results, omit the modulus

Common Mistakes

• Using pow() with three arguments and passing floats — will raise TypeError
• Forgetting to use ** instead of ^ for exponentiation (Python uses ^ as bitwise XOR)

Interview Tip

In competitive programming and coding interviews, pow(a, b, c) is a fast and safe way to compute large powers under a modulus, avoiding overflow errors.

Summary

• pow(x, y) returns x**y
• pow(x, y, z) returns (x**y) % z efficiently
• Useful in math, encryption, and large number problems

Practice Problem

Write a program to compute the last digit of ab for given input values:

a = int(input("Enter base: "))
b = int(input("Enter exponent: "))
print("Last digit is:", pow(a, b, 10))