print("The list is empty") 这种方法虽然冗长,但在某些情况下可能更直观。 判断空字典 同样的方法也适用于字典: some_dict = {} if len(some_dict) == 0: print("The dictionary is empty") 通过判断长度,我们可以明确地知道字典中是否包含任何元素。 四、使用'TRUTHY'和'FALSY'值判断空值 在Python中,...
Python中的很多对象在布尔上下文中都有自然的真值(truthy)或假值(falsy)。空字符串""、空列表[]、空字典{}、空元组()等都被视为假值(falsy),因此可以直接在if语句中使用它们来判断: python empty_str = "" if not empty_str: print("empty_str为空") empty_list = [] if not empty_list: print("...
具体参考以下示例: 以上这两个例子表明,这种方式会返回第一个非错误值(non-falsy object)。那么,下面这个代码又会返回什么结果呢? 如果运行这些代码,你会发现,what在这里返回的是空列表(empty list)。我们把这个结果的原因留到以后讨论。接下来,观察下面这个使用and逻辑运算符的示例: 仔细察看这些例子,看看你是否知...
ifnotmy_list:print("List is empty") This is using theTruth Value Testingin Python, also known as implicit booleaness or truthy/falsy value testing. Among other rules it defines that empty sequences and collections like'', (), [], {}, set(), range(0)are all considered false. ...
另一个不便是第一个常量会有一个值0,在 Python 中是 falsy。在某些情况下,这可能是一个问题,尤其是那些涉及到布尔测试的情况。**注意:**如果您使用的是 Python 之前的版本,那么您可以通过安装 enum34 库来创建枚举,这是标准库enum的一个反向移植。第三方库也是你的一个选择。
all([]) returns True since the iterable is empty. all([[]]) returns False because the passed array has one element, [], and in python, an empty list is falsy. all([[[]]]) and higher recursive variants are always True. This is because the passed array's single element ([[...]...
A non-empty list is truthy, and the while statement treats it as True. The value returned by len() determines the truthiness of a sequence. A sequence is truthy when len() returns any non-zero integer and falsy when len() returns 0....
This example shows all with different list configurations. Note how it handles empty lists (returns True) and various truthy/falsy values. The function follows Python's truthiness rules: 0, empty strings, empty containers are False, while other values are True. ...
For example an empty list/sequences [], empty dictionaries {} None, False, Zero for numeric types, are considered “falsy”. On the other hand, almost everything else is considered “truthy”. # bad x = True y = 0 if x == True: ...
3. use the falsy & truthy concepts For example an empty list/sequences [], empty dictionaries {} None, False, Zero for numeric types, are considered “falsy”. On the other hand, almost everything else is considered “truthy”.