python - 在python断言中，断言失败时如何打印条件？

Question

在 Python 中，我可以这样做:

assert result==100, "result should be 100"

但这是多余的，因为我必须输入两次条件。

有没有办法告诉 Python 在断言失败时自动显示条件？

Answer 1

来自 Jupyter 笔记本

这发生在回溯中。例如:

x = 2
assert x < 1
---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
<ipython-input-5-0662b7144a79> in <module>()
      1 x = 2
----> 2 assert x < 1

AssertionError: 

但是，将发生此错误的原因人性化(即用文字解释)是一种很好的做法。通常，我用它来反馈有用的信息。例如:

x = 2
assert x < 1, "Number is not less than 1: {0}".format(x)
---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
<ipython-input-4-bd4b9b15ccc2> in <module>()
      1 x = 2
----> 2 assert x < 1, "Number is not less than 1: {0}".format(x)

AssertionError: Number is not less than 1: 2

从命令行

回溯仍然会发生这种情况。例如:

H:\>python assert.py
Traceback (most recent call last):
  File "assert.py", line 1, in <module>
    assert 2 < 1
AssertionError

适用于所有环境的解决方案

使用 traceback模块。详情请查看 How to handle AssertionError in Python and find out which line or statement it occurred on?的回答