Python 断言发生了某种错误
给定以下代码:Python 断言发生了某种错误,python,testing,try-catch,throw,assertion,Python,Testing,Try Catch,Throw,Assertion,给定以下代码: def fun(param): if param == 'a': assert False else: return None # fun('a') THIS THROWS AN AssertionError # PSEUDOCODE FOR WHAT I WANT TO DO: # assert (fun('a') throws an AssertionError) assert fun('b') == None 我如何断言第
def fun(param):
if param == 'a':
assert False
else:
return None
# fun('a') THIS THROWS AN AssertionError
# PSEUDOCODE FOR WHAT I WANT TO DO:
# assert (fun('a') throws an AssertionError)
assert fun('b') == None
我如何断言第一个函数调用(fun('a'))将给我一个AssertionError?我需要试一试,还是有更优雅的方式?您可以使用:
import pytest
...
with pytest.raises(AssertionError):
fun('a')
如果fun('a')
未引发断言错误,则会引发错误
或者,如果您使用的是unittest
,并且您在TestCase
中,则可以使用:
另外,正如其他答案所提到的,你最好是提出一个错误,而不是断言False
。如果您确实引发了一个错误,您可以引发一个错误,告诉用户更多错误,或者引发您自己的自定义异常:
import pytest
class AError(Exception):
pass
def fun(param):
if param == 'a':
raise AError("You passed 'a'; don't do that!")
else:
return None
with pytest.raises(AError):
fun('a')
抛出断言可能是更好的方法。例如:
def fun(param):
if param == 'a':
raise AssertionError('Param is equal to \'a\'.')
else:
return None
try:
fun('b')
print('Equalling \'b\' worked fine.')
fun('a')
print('This line is not printed...')
except AssertionError as err:
print('An assertion error has been raised:')
print(err)
给出:
Equalling 'b' worked fine.
An assertion error has been raised:
Param is equal to 'a'.
这很好地回答了我的问题。因为我很忙,所以不能马上回复。谢谢!
Equalling 'b' worked fine.
An assertion error has been raised:
Param is equal to 'a'.