In Python, you can use the str.startswith() and str.endswith() methods to check if a string begins or ends with a specific substring.

Code Example:

def check_string(s, start_sub, end_sub):
    starts = s.startswith(start_sub)
    ends = s.endswith(end_sub)
    return starts, ends

# Example usage
sentence = "Hello, world!"
print(check_string(sentence, "Hello", "world!"))  # Output: (True, True)

This function returns True if the string starts with the given substring and True if it ends with the specified substring.