Python - 确保变量保持正数 [英] Python - Ensuring a variable holds a positive number

问题描述

我正在寻找一种优雅的方法来确保给定的变量保持正值.

I am looking for an elegant way to ensure that a given variable remains positive.

我有两个保存正浮点数的变量，我根据某些条件将它们递减.最后我想保证我仍然有正数(或最多 0).伪代码如下所示:

I have two variables that hold positive float numbers and I decrement them according to certain conditions. At the end I want to guarantee that I still have positive numbers (or 0 at most). The pseudo code looks something like this:

list = [...]

value1 = N
value2 = M

for element in list:
    if ... :
        value1 -= X
    if ... :
        value2 -= Y

除了在末尾添加两个 ifs 之外，还有更优雅的解决方案吗?

Is there a more elegant solution than just adding two ifs at the end?

推荐答案

我不清楚你想做什么——变量可以是负数，也可以不是.

I am unclear as to what you want to do -- either the variables can be negative, or they can't.

• 如果您要反复递减一个变量，并且在此之后您想检查它们是否为负，请使用 if 来执行 - 这就是它的用途！

• If you are decrementing a variable repeatedly and after doing so you want to check whether they are negative, do so with an if -- that's what it's for!

if value < 0: # do stuff

如果您认为变量应该永远不会是负数，并且您想在代码中的代码中断言这一事实​​，那么您可以

If you think the variables should never be negative and you want to assert this fact in the code in the code, you do

assert value > 0

如果条件不成立，可能会引发 AssertionError(当 Python 不在调试模式下运行时，assert 不会执行).

which may raise an AssertionError if the condition doesn't hold (assert will not execute when Python is not run in debug mode).

如果您希望变量在已减小到 0 以下时为 0，请执行

If you want the variable to be 0 if it has been decreased below 0, do

value = max(value, 0)

如果您希望变量为负数而否定，请执行

If you want the variable to be negated if it is negative, do

value = value if value > 0 else -value

或

value = abs(value)

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