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Medium

## Instructions

Convert a number, represented as a sequence of digits in one base, to any other base.

Implement general base conversion. Given a number in base a, represented as a sequence of digits, convert it to base b.

### Note

• Try to implement the conversion yourself. Do not use something else to perform the conversion for you.

In positional notation, a number in base b can be understood as a linear combination of powers of b.

The number 42, in base 10, means:

(4 * 10^1) + (2 * 10^0)

The number 101010, in base 2, means:

(1 * 2^5) + (0 * 2^4) + (1 * 2^3) + (0 * 2^2) + (1 * 2^1) + (0 * 2^0)

The number 1120, in base 3, means:

(1 * 3^3) + (1 * 3^2) + (2 * 3^1) + (0 * 3^0)

I think you got the idea!

Yes. Those three numbers above are exactly the same. Congratulations!

### Exception messages

Sometimes it is necessary to raise an exception. When you do this, you should always include a meaningful error message to indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. For situations where you know that the error source will be a certain type, you can choose to raise one of the built in error types, but should still include a meaningful message.

This particular exercise requires that you use the raise statement to "throw" a `ValueError` for different input and output bases. The tests will only pass if you both `raise` the `exception` and include a meaningful message with it.

To raise a `ValueError` with a message, write the message as an argument to the `exception` type:

``````# for input.
raise ValueError("input base must be >= 2")

# another example for input.
raise ValueError("all digits must satisfy 0 <= d < input base")

# or, for output.
raise ValueError("output base must be >= 2")
``````
Last updated 22 June 2022
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