assert

A coworker has added the assert command a few times within our libraries in places where I would have used an if statement and thrown an exception. (I had never even heard of assert before this.) Here is an example of how he used it: assert('isset($this->records); /* Records must be set before this is called. */'); I would have done: if (!isset($this->records)) { throw new Exception('Records must be set before this is called'); } From reading the PHP docs on assert , it looks like it's recommended that you make sure assert is active and add a handler before using assert. I can't find a place

inal作用域的代码一定会被执行吗？ 正常的情况下，finally作用域的代码一定会被执行的，不管是否发生异常。哪怕是调用了sys.exit函数，finally也是会被执行的，那怎么样才能让finally代码不执行了。 上面的代码主要是通过让流程停滞在try作用域里，从而实现了需求。上面的代码不排除有点投机取巧的意思，但是我们实习了题目的需求不是吗。 可以对含有任意的元素的list进行排序吗？ 正常情况下： 那是不是以为着，任何list都可以调用sort函数进行排序了？ python里1j是一个特殊符号代表-1的平方根，出现这个问题的原因是sort函数调用的对象的__lt__函数来比较两个对象的，而复杂的数字类型是不可比较的，也就说没有实现__lt__函数，所以比较不了。因此，对于list里包含的对象如果都是可以比较的，也就是说实现了__lt__函数，那么对list调用sort函数是没问题的。 Python可是使用++x或者x++之类的操作吗？ ++x操作是可以的，但是这个操作产生的结果和C语言里该操作产生的结果是不一样的，Python里++x操作里的加好只是一个一元操作符，所以，++x等价于+(+x)，所以++x == x。 x++操作是不合法的，虽然有些情况下，x++看着是合法的，比如：x++-y，但其实这个表达式等价于x+(+(-y)) = x-y，所以正常情况下，x+

Every C programmer can determine the number of elements in an array with this well-known macro: #define NUM_ELEMS(a) (sizeof(a)/sizeof 0[a]) Here is a typical use case: int numbers[] = {2, 3, 5, 7, 11, 13, 17, 19}; printf("%lu\n", NUM_ELEMS(numbers)); // 8, as expected However, nothing prevents the programmer from accidentally passing a pointer instead of an array: int * pointer = numbers; printf("%lu\n", NUM_ELEMS(pointer)); On my system, this prints 2, because apparently, a pointer is twice as large as an integer. I thought about how to prevent the programmer from passing a pointer by

Let's say that I have a class Suit and four subclasses of suit: Heart, Spade, Diamond, Club. class Suit: ... class Heart(Suit): ... class Spade(Suit): ... class Diamond(Suit): ... class Club(Suit): ... I have a method which receives a suit as a parameter, which is a class object, not an instance. More precisely, it may receive only one of the four values: Heart, Spade, Diamond, Club. How can I make an assertion which ensures such a thing? Something like: def my_method(suit): assert(suit subclass of Suit) ... I'm using Python 3. You can use issubclass() like this assert issubclass(suit, Suit) .

The JUnit framework contains 2 Assert classes (in different packages, obviously) and the methods on each appear to be very similar. Can anybody explain why this is? The classes I'm referring to are: junit.framework.Assert and org.junit.Assert . Mnementh The old method (of JUnit 3) was to mark the test-classes by extending junit.framework.TestCase . That inherited junit.framework.Assert itself and your test class gained the ability to call the assert methods this way. Since version 4 of JUnit, the framework uses Annotations for marking tests. So you no longer need to extend TestCase . But that