Another way which also works but is not necessary is to check if the length is equal to 0: iflen(my_list)==0:print("List is empty") Although the first approach is considered to be morePythonic, some people prefer the explicit second approach. ...
之所以在写法二中可以用if直接判断列表a是否为空,是因为对于list来说,它没有内建方法__bool__(),而有内建方法__len__(),最后通过判断list长度是否为 0 来得出true或者false的,一旦为空,则判断结果为false
A more explicit way to check if a list is empty is to use Python's built-inlen()function, which returns the number of items in a list. Here's how you can uselen()to check if a list is empty: my_list=[]iflen(my_list)==0:print("The list is empty")else:print("The list is...
# Define a function named 'is_Sublist' that checks if list 's' is a sublist of list 'l' def is_Sublist(l, s): sub_set = False # Initialize a flag 'sub_set' to indicate whether 's' is a sublist of 'l # Check if 's' is an empty list; in this case, 's' is a sublist...
当数据不应该被复制时,例如因为数据太大或者函数设计需要在原地更改数据以使调用者受益时,调用list()会很糟糕。在这种情况下,像isinstance(x, abc.MutableSequence)这样的运行时检查将是一个好方法。如果你担心得到一个无限生成器——这不是一个常见问题——你可以先调用len()来检查参数。这将拒绝迭代器,同时安全...
if sys.version_info >= (3,): def clear(self) -> None: ... def copy(self) -> List[_T]: ... def append(self, object: _T) -> None: ... def extend(self, iterable: Iterable[_T]) -> None: ... def pop(self, index: int = ...) -> _T: ... ...
reversed()和sorted()同样表示对列表/元组进行倒转和排序,reversed()返回一个倒转后的迭代器(上文例子使用list()函数再将其转换为列表);sorted()返回排好序的新列表。 列表和元组存储方式的差异 前面说了,列表和元组最重要的区别就是,列表是动态的、可变的,而元组是静态的、不可变的。这样的差异,势必会影响两者...
if freqs[k] == best: words.append(k) return (words, best)---返回值是一个列表,里面有一个或者多个并列的element,以及对应的数值,这个是int。def words_often (freqs, minTimes): --- a dictionary, and a minimum number of times result = [] ---an empty list ...
numbers = [2, 4, 6, 8, 1] for number in numbers: if number % 2 == 1: print(number) break else: print("No odd numbers") 如果找到了奇数,就会打印该数值,并且执行break语句,跳过else语句。没有的话,就不会执行break语句,而是执行else语句。 ▍2、从列表中获取元素,定义多个变量 my_list = ...
>>> for item in empty_list:... if not item:... print(f'Do something with the{type(item)}')...Do something with the <class 'tuple'> Do something with the <class 'str'> Do something with the <class 'list'> Do something with the <class 'dict'> Do something with the <...