When Is A Bug Not A Bug in Python?

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While writing a chess program in Python as a learning exercise, I had two separate functions for converting a position from an algebraic notation string, 'a1', to a tuple, (97, 1), and vice versa. I later merged the two functions into a static method for the Board class. The code works. I should have left it at that and move on.

I found any interesting situation when refactoring the code to work with @functools.singledispatch and @staticmethod in a class. The code worked but I was using the wrong single dispatch decorator. When is a bug not a bug?

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The Incompatible Type Assignment Error in Mypy

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I’m writing a chess program in Python as a learning exercising. Not surprisingly, mypy, the static type checker, complained about my code with yet another incomprehensible error message. Here’s a quick-and-dirty fix for the incompatible type assignment error.

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Fixing A String Issue with Enum.name in MyPy

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While cleaning up code in my chess program that I’m writing in Python as a learning exercise, I came across yet another problem with the mypy static type checker. This time with the Enum.name attribute.

color = Color(self._color).name.capitalize()

The statement worked but mypy reported an error message.

error: Item “None” of “Optional[str]” has no attribute “capitalize”

I came up with a solution for that problem.

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Fixing “None” Not Callable Error in Mypy

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The mypy static type checker always complain about using a dictionary to call functions. Especially this code segment from my chess program that I’m writing in Python as a learning exercise.

status = {Bishop: self.validate_move_bishop,
King: self.validate_move_king,
Knight: self.validate_move_knight,
Pawn: self.validate_move_pawn,
Queen: self.validate_move_queen,
Rook: self.validate_move_rook,
}.get(type(self._board[start]))(start, end)

This message, error: “None” not callable, always leave me cross-eyed at times. I came up with a solution for that problem.

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Fixing The Incompatible Dunder Method Error in Mypy

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While cleaning up my code in a chess program that I’m writing in Python as a learning exercise, I created an Enum class to represent the starting ranks for certain pieces on the board. Since I wanted the Enum to also behave like a list, I added that to the class definition. The mypy static type checker reported an incompatible __hash__ dunder method error between list and Enum. I came up with a solution for that problem.

Read my essay and follow me on Medium. Your support is greatly appreciated.