python - 为什么没有引发 ValueError ？

Question

Python 文档指出:

所以我的代码是:

print(pow(-2,2.1))

这段代码应该引发 ValueError，因为 -2 和 2 是有限的，-2 是负数，并且 2.1 不是整数 - 因此 pow(-2,2.1) 是未定义的。

Answer 1

您将内置 pow 函数与 math.pow 的文档混淆了

请参阅此处了解内置 pow 函数: https://docs.python.org/3/library/functions.html#pow

Return x to the power y; if z is present, return x to the power y, modulo z (computed more efficiently than pow(x, y) % z). The two-argument form pow(x, y) is equivalent to using the power operator: x**y.

The arguments must have numeric types. With mixed operand types, the coercion rules for binary arithmetic operators apply. For int operands, the result has the same type as the operands (after coercion) unless the second argument is negative; in that case, all arguments are converted to float and a float result is delivered. For example, 102 returns 100, but 10-2 returns 0.01. If the second argument is negative, the third argument must be omitted. If z is present, x and y must be of integer types, and y must be non-negative.

还值得注意的是，内置 pow 函数的结果与使用 ** 的结果相同，即pow(-2,2.1) 相当于 (-2) ** 2.1