In Python, you can decode a Base64 encoded string using the base64 package.

Using base64.b64decode()

This is the standard and most straightforward method using the base64 module.

import base64

encoded_data = 'SGVsbG8sIFdvcmxkIQ=='
decoded_data = base64.b64decode(encoded_data)
print(decoded_data.decode('utf-8'))  # Output: Hello, World!

Using base64.urlsafe_b64decode()

If your Base64 encoded data is URL-safe, meaning it uses - instead of + and _ instead of /, you should use urlsafe_b64decode(). This function is similar to b64decode() but supports URL and filesystem safe alphabet.

import base64

encoded_data = 'SGVsbG8sIFdvcmxkIQ=='.replace('+', '-').replace('/', '_')  # Making it URL-safe for demonstration
decoded_data = base64.urlsafe_b64decode(encoded_data)
print(decoded_data.decode('utf-8'))  # Output should still be: Hello, World!