Using in-line variable substitution in Calculate Field Python within ModelBuilder gives a correct but potentially misleading error message which gives the appearance the tool fails but it works as intended.

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Solución alternativa

Ignore the error message but if there is other things wrong with the calculation this is to be overlooked.

Note: %-% is not valid Python, the validator correctly throws an error. Writing proper Python takes care of this. Enclose the variable needed to replace in a string.

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