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Asked: 2024-09-26T14:14:50+05:30 In:

How to Convert Strings Between Custom Number Bases with Error Handling in Python?

I’ve been diving into base conversion lately and stumbled upon a challenge that’s been rolling around in my mind. So, here’s the thing: I want to convert numbers represented as strings from one base to another, but with a little twist that makes things interesting!

Imagine you have a string that represents a number in base B1, and you need to convert it into base B2. The catch is that the number might contain characters beyond just 0-9 or A-Z. For example, let’s say we’re working with characters from a custom alphabet, like `0123456789abcdefg`, which gives us a base of 17. So, numbers can go up to 16 (which would be ‘g’ in this case).

Here’s a simple example to get your gears turning. Let’s say we take the string “1g” in base 17. That means we have 1*17 + 16*1 = 33 in decimal. Now, if we wanted to convert it to base 10 (which of course is just base 10), we’d output “33”. But what if we wanted to convert it to base 5? You’d have to split it up further, since base 5 uses only the digits 0-4.

Now, here’s where I’d love to see your input! How would you approach this problem? Can you come up with a neat function or method that takes in these strings and handles the conversion smoothly? And if possible, could you also think about error handling for cases where the input might not be a valid representation in the specified base?

Maybe you could share your code or thought process on how to manage the base conversions and handle those edge cases, like if the input string is something that goes beyond the bounds of the specified base. Plus, if you could throw in some test cases that cover a variety of scenarios (especially trickier ones), that would be awesome!

Looking forward to your ideas! Let’s get some clever solutions going!

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    2 Answers






    1. Base Conversion

      Base Conversion Challenge

      Here’s a basic idea of how you could tackle the base conversion task!





    2. Base Conversion Function

      To convert a string representing a number in base B1 to base B2, we can approach this problem by first defining a function that validates the input and converts it to decimal, and then converts that decimal number to the desired base. Below is a Python function illustrating this concept:

          
def base_conversion(string_num, base_from, base_to, alphabet):
    # Validate input
    if base_from > len(alphabet) or base_to > len(alphabet):
        raise ValueError(f"Base must be <= {len(alphabet)}")
    
    for char in string_num:
        if char not in alphabet[:base_from]:
            raise ValueError(f"Invalid character '{char}' for base {base_from}")

    # Convert string to decimal
    decimal_value = sum(alphabet.index(char) * (base_from ** i) for i, char in enumerate(reversed(string_num)))

    # Convert decimal to target base
    if decimal_value == 0:
        return alphabet[0]
    
    result = []
    while decimal_value > 0:
        result.append(alphabet[decimal_value % base_to])
        decimal_value //= base_to
        
    return ''.join(reversed(result))

# Test cases
alphabet = '0123456789abcdefg'  # base 17
print(base_conversion("1g", 17, 10, alphabet))  # Outputs: "33"
print(base_conversion("33", 10, 5, alphabet))   # Outputs: "123"
print(base_conversion("10", 5, 10, alphabet))    # Outputs: "5"

      This code validates the input, converts the original number to decimal, and then converts the decimal number to the desired base using a custom alphabet. Each step ensures that any potential errors are managed through appropriate checks, thus improving the robustness of the function. You can expand the test cases to cover various scenarios, including edge cases with invalid characters or exceeding bases, to see how the function handles them.


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