[Python] Why does Python's modulus operator (%) not match the Euclidean definition?

Discussão em 'Python' iniciado por Stack, Julho 19, 2025.

  1. Stack

    Stack Membro Participativo

    Euclidean definition says,


    Given two integers a and b, with b ≠ 0, there exist unique integers q and r such that a = bq + r and 0 ≤ r < |b|, where |b| denotes the absolute value of b.
    ​

    Based on below observation,

    >>> -3 % -2 # Ideally it should be (-2 * 2) + 1
    -1
    >>> -3 % 2 # this looks fine, (-2 * 2) + 1
    1
    >>> 2 % -3 # Ideally it should be (-3 * 0) + 2
    -1


    looks like the % operator is running with different rules.

    • link1 was not helpful,
    • link2 gives recursive answer, because, as I do not understand how % works, it is difficult to understand How (a // b) * b + (a % b) == a works

    My question:

    How do I understand the behavior of modulo operator in python? Am not aware of any other language with respect to the working of % operator.

    Continue reading...

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