How to use mod in python

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MOD is the modulo operator.

Syntax

MOD ( a, b)

Usually the modulo operation (mod) and the remainder (rem) operation are confused, because in most programming languages, both The '%' symbol indicates modulo or remainder operation. Here I would like to remind everyone to pay close attention to the specific meaning of the '%' operator in the current environment, because when there are negative numbers, the results of the two are different.

For integer numbers a and b, the methods of modulo operation or remainder operation are:

1. Find the integer quotient: c = a/b;

2. Calculate the modulus or number: r = a - c*b.

The modular operation and the remainder operation are different in the first step: finding the remainder When calculating the value of c, the operation rounds toward 0 (fix() function); while when the modulo operation calculates the value of c, it rounds toward negative infinity (floor() function).

Therefore, when the signs of a and b are the same, the values ​​of c obtained by the modulo operation and the remainder operation are the same, so the results are consistent. But when the symbols are inconsistent, the results are different. The sign of the modulo operation result is the same as b, and the sign of the remainder operation result is the same as a.

In C language, the % symbol represents the remainder operation, and in python script, % represents the modulus.

(Usually b is not allowed to be a negative number in the modulo operation, but in python 2.5.1, % can be followed by a negative number, because the result of division in the python language is rounded towards 0, so the calculation result is Modulo!)

(1) When a and b have the same sign, the result is equivalent to the remainder operation, that is, r = a-a/b;

Result rules:

同正为正，同负为负。

Example:

1 % 2 == 1；-1 % -2 == -1.

(2)When a and b have different signs,

①Remainder operation, ren(5,-3)

c = fix(a/b); // c = -1
r = a-b*c; // r = 2

② Modulo operation, mod(5,-3)

c = floor(a/b);//c=-2
r = a-b*c; //r = -1

Result rules:

当 a > b 时，a % b == 1 or 0;
当 a < b 时，a % b == -1 or 0;

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