assert

一般用法是：

assert condition

用来让程序测试这个condition，如果condition为False则抛出一个AssertionError，逻辑上等同于

if not condition:    raise AssertionError()

比如下面的例子

>>> assert 1==1>>> assert 1==0Traceback (most recent call last):  File "
    
     ", line 1, in 
     
          assert 1==0AssertionError>>> assert True>>> assert FalseTraceback (most recent call last):  File "
      
       ", line 1, in 
       
            assert FalseAssertionError>>> assert 3<2Traceback (most recent call last):  File "
        
         ", line 1, in 
         
           assert 3<2AssertionError