Convert a Binary Number to Decimal

Binary numbers, the foundation of digital computing, represent data using only two digits: 0 and 1. Understanding how to convert these binary representations into their decimal (base-10) equivalents is crucial for anyone working with computer science or programming. This post will guide you through several effective methods for converting binary numbers to decimal in Python, complete with code examples and explanations.

Method 1: Using the int() function

Python’s built-in int() function provides a straightforward way to perform this conversion. The int() function accepts a second argument specifying the base of the number you’re converting. For binary to decimal conversion, you’ll use base 2.

binary_number = "101101"  # Example binary number

decimal_number = int(binary_number, 2)

print(f"The decimal equivalent of {binary_number} is: {decimal_number}") 

This code snippet takes the binary string “101101”, passes it to int() with base 2, and directly outputs the decimal equivalent. This is the most concise and efficient approach.

Method 2: Manual Conversion using a Loop

For a deeper understanding of the underlying process, let’s implement the conversion manually using a loop. This method iterates through the binary digits, multiplying each digit by the corresponding power of 2 and summing the results.

binary_number = "101101"
decimal_number = 0
power = 0

for digit in reversed(binary_number):
    if digit == '1':
        decimal_number += 2**power
    power += 1

print(f"The decimal equivalent of {binary_number} is: {decimal_number}")

This code first reverses the binary string to easily work with powers of 2 from right to left. It then iterates, adding 2 raised to the power of the digit’s position if the digit is ‘1’.

Method 3: Using the bin() function (Reverse Conversion)

While not directly converting binary to decimal, the bin() function offers a useful demonstration. It converts an integer into its binary representation. You can use this to verify your conversion results.

decimal_number = 45

binary_number = bin(decimal_number)

print(f"The binary representation of {decimal_number} is: {binary_number[2:]}") # [2:] removes the "0b" prefix

This code converts the decimal number 45 to its binary equivalent. Note that the [2:] slicing removes the “0b” prefix that bin() adds to indicate a binary number. You can combine this with methods 1 or 2 to create a self-checking function.

Handling Errors: Invalid Binary Input

It’s crucial to handle potential errors, such as non-binary characters in the input string. You can achieve this using a try-except block:

def binaryToDecimal(binary):
    try:
        return int(binary, 2)
    except ValueError:
        return "Invalid binary string"

print(binaryToDecimal("101101")) # Output: 45
print(binaryToDecimal("101121")) # Output: Invalid binary string

This function gracefully handles invalid input, returning an appropriate message instead of crashing. Robust error handling is essential for writing reliable code.