57 lines
2.2 KiB
Markdown
57 lines
2.2 KiB
Markdown
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# Grains
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Welcome to Grains on Exercism's Python Track.
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If you need help running the tests or submitting your code, check out `HELP.md`.
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## Instructions
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Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
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There once was a wise servant who saved the life of a prince.
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The king promised to pay whatever the servant could dream up.
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Knowing that the king loved chess, the servant told the king he would like to have grains of wheat.
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One grain on the first square of a chess board, with the number of grains doubling on each successive square.
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There are 64 squares on a chessboard (where square 1 has one grain, square 2 has two grains, and so on).
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Write code that shows:
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- how many grains were on a given square, and
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- the total number of grains on the chessboard
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## Exception messages
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Sometimes it is necessary to [raise an exception](https://docs.python.org/3/tutorial/errors.html#raising-exceptions). 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](https://docs.python.org/3/library/exceptions.html#base-classes), but should still include a meaningful message.
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This particular exercise requires that you use the [raise statement](https://docs.python.org/3/reference/simple_stmts.html#the-raise-statement) to "throw" a `ValueError` when the square input is out of range. The tests will only pass if you both `raise` the `exception` and include a message with it.
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To raise a `ValueError` with a message, write the message as an argument to the `exception` type:
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```python
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# when the square value is not in the acceptable range
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raise ValueError("square must be between 1 and 64")
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```
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## Source
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### Contributed to by
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- @behrtam
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- @BethanyG
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- @cmccandless
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- @denislooby
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- @Dog
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- @kytrinyx
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- @lowks
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- @MojitoMonday
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- @N-Parsons
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- @pheanex
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- @sdublish
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- @sjakobi
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- @smalley
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- @tqa236
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- @yawpitch
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### Based on
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The CodeRanch Cattle Drive, Assignment 6 - https://coderanch.com/wiki/718824/Grains
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