blocks|key|440509|text|我的非常黑客的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|440510|def+my_assert(condition):
++++if+not+eval(condition):
++++++++#+error+stuff|code-block|syntax|javascript|440511|然后通过将条件放在引号中来使用它。然后它就是一个可以在错误消息中打印的字符串。|440512|或者，如果您希望它实际引发一个AssertionError|offset|length|style|CODE|440513|def+my_assert(condition):
++++if+not+eval(condition):
++++++++raise+AssertionError(condition)|440514|entityMap^0|0|0|0|F|E|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|V|8|@$K|W|L|X|M|N]]|9|@]|A|$]]|$1|O|3|P|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

My very hackish solution:

<pre><code>def my_assert(condition):
 if not eval(condition):
 # error stuff
</code></pre>

Then use it by placing the condition in quotation marks. It is then a string that can be printed in the error message.

Or, if you want it to actually raise an <code>AssertionError</code>:

<pre><code>def my_assert(condition):
 if not eval(condition):
 raise AssertionError(condition)
</code></pre>

blocks|key|1581933|text|AssertionError就像python中的任何其他异常一样，而assert是一个简单的语句，等同于|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1581934|if+__debug__:
++++if+not+expression:+raise+AssertionError|code-block|syntax|javascript|1581935|或|1581936|if+__debug__:
++++if+not+expression1:+raise+AssertionError(expression2)|1581937|因此，您可以在断言中添加第二个参数，以获得额外的输出|1581938|from+sys+import+exc_info
from+traceback+import+print_exception
#+assertions+are+simply+exceptions+in+Python
try:
++++assert+False,+"assert+was+false"
except+AssertionError:
++++print_exception(*exc_info())|1581939|输出|1581940|Traceback+(most+recent+call+last):
++File+"<stdin>",+line+2,+in+<module>
AssertionError:+assert+was+false|1581941|entityMap^0|Y|6|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|14|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|16|8|@]|D|@]|E|$]]|$1|U|3|V|5|H|7|17|8|@]|D|@]|E|$I|J]]|$1|W|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|X|$]]

AssertionError is just like any other exception in python, and <code>assert</code> is a simple statement that is equivalent to

<pre><code>if __debug__:
 if not expression: raise AssertionError
</code></pre>

or

<pre><code>if __debug__:
 if not expression1: raise AssertionError(expression2)
</code></pre>

so you can add a second parameter to your assertion to have additional output

<pre><code>from sys import exc_info
from traceback import print_exception
# assertions are simply exceptions in Python
try:
 assert False, "assert was false"
except AssertionError:
 print_exception(*exc_info())
</code></pre>

outputs

<pre><code>Traceback (most recent call last):
 File "&lt;stdin&gt;", line 2, in &lt;module&gt;
AssertionError: assert was false
</code></pre>

blocks|key|440550|text|如果你确定要测试的表达式是安全的，你可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|440551|文件my_assert.py：|440552|import+sys

def+my_assert(condition):
++++caller+=+sys._getframe(1)
++++if+not+eval(condition,+caller.f_globals,+caller.f_locals):
++++++++raise+AssertionError(repr(condition)+%2B+"+on+line+"+%2B
+++++++++++++++++++++++++++++str(caller.f_lineno)+%2B+'+in+'+%2B
+++++++++++++++++++++++++++++caller.f_code.co_name)|code-block|syntax|javascript|440553|文件test_my_assert.py：|440554|from+my_assert+import+my_assert

global_var+=+42

def+test():
++++local_var+=+17
++++my_assert('local_var*2+<+global_var')+#+OK
++++my_assert('local_var+>+global_var')

test()|440555|输出：|440556|Traceback+(most+recent+call+last):
++File+"test_my_assert.py",+line+10,+in+<module>
++++test()
++File+"test_my_assert.py",+line+8,+in+test
++++my_assert('local_var+>+global_var')
++File+"my_assert.py",+line+8,+in+my_assert
++++caller.f_code.co_name)
AssertionError:+'local_var+>+global_var'+on+line+8+in+test|440557|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

If you're sure the expression to test is secure you could do something like this:

File my_assert.py:

<pre><code>import sys

def my_assert(condition):
 caller = sys._getframe(1)
 if not eval(condition, caller.f_globals, caller.f_locals):
 raise AssertionError(repr(condition) + " on line " +
 str(caller.f_lineno) + ' in ' +
 caller.f_code.co_name)
</code></pre>

File test_my_assert.py:

<pre><code>from my_assert import my_assert

global_var = 42

def test():
 local_var = 17
 my_assert('local_var*2 &lt; global_var') # OK
 my_assert('local_var &gt; global_var')

test()
</code></pre>

Output:

<pre class="lang-none prettyprint-override"><code>Traceback (most recent call last):
 File "test_my_assert.py", line 10, in &lt;module&gt;
 test()
 File "test_my_assert.py", line 8, in test
 my_assert('local_var &gt; global_var')
 File "my_assert.py", line 8, in my_assert
 caller.f_code.co_name)
AssertionError: 'local_var &gt; global_var' on line 8 in test
</code></pre>

I'm trying to implement an assert function. How can I get the text of the failing condition into the error message? If I have to parse it from the backtrace, can I portably rely on anything about the format of frames?

Implementing C-like assert

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在尝试实现一个断言函数。如何将失败条件的文本添加到错误消息中？如果我必须从回溯中解析它，我可以依赖任何关于帧格式的东西吗？

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