如何在Python的assert语句中使用小于和等于

Question

当我运行下面的代码时：

growthRates = [3, 4, 5, 0, 3]
for each in growthRates:
    print each
    assert growthRates >= 0, 'Growth Rate is not between 0 and 100'
    assert growthRates <= 100, 'Growth Rate is not between 0 and 100'

我得到的结果是：

3
Traceback (most recent call last):
  File "ps4.py", line 132, in <module>
    testNestEggVariable()
  File "ps4.py", line 126, in testNestEggVariable
    savingsRecord = nestEggVariable(salary, save, growthRates)
  File "ps4.py", line 106, in nestEggVariable
    assert growthRates <= 100, 'Growth Rate is not between 0 and 100'
AssertionError: Growth Rate is not between 0 and 100

这是为什么呢？

Answer 1

这段代码的意思是：我们在检查每个值是否都大于等于0。用简单的话说，就是我们希望确保每个值都是非负的（也就是0或更大）。

而后面那句“not assert (growthRates >= 0)”则表示我们不想检查“增长率是否大于等于0”。这句话带着一点幽默的语气，意思是说我们不关心增长率的情况。

Answer 2

assert 0 <= each <= 100, 'Growth Rate %i is not between 0 and 100.' % each

你的断言当然不会失败，但现在的 growthRates > 100 是因为 growthRates 是一个列表，而 0 是一个整数。在比较时，'列表' 是大于 '整数' 的。

Answer 3

要做的：

assert each >= 0, 'Growth Rate is not between 0 and 100'

不要做的：

assert growthRates >= 0, 'Growth Rate is not between 0 and 100'