importtimeitdefusing_is_none(variable):returnvariableisNonedefusing_if_not_none(variable):returnnotvariable variable =Noneprint("Using 'is None':", timeit.timeit(lambda: using_is_none(variable), number=1000000))print("Using 'if not None':", timeit.timeit(lambda: using_if_not_none(variable)...
在python中有两个身份运算符,一个是is另外一个是is not。 作用:身份运算符用于比较两个对象的内存地址是否一致——是否对同一个对象的引用。 在python中针对None比较时,建议使用is判断。 一、Is 与 == 的区别: is 用于判断两个变量引用对象是否为同一个。 == 用于判断引用变量的值是否相等。 代码验证: 代码...
x = None if x : print("if x ") # 此时无打印结果 if x is not None: print("if x is not None")# 此时打印结果为 if x is not None 此时如果是bool(x)的话, >>> bool(x) False (3)x = 12 x = 12 if x : print("if x ") # 此时打印结果为:if x if x is not None: pr...
1. 使用is关键字判断变量是否为None 在Python中,None表示空值。我们可以使用is关键字来判断变量是否为None。示例代码如下: ifvariableisNone:print("变量为空")else:print("变量不为空") 1. 2. 3. 4. 其中,variable是需要判断的变量。 2. 使用not关键字判断变量是否为空 在Python中,not关键字可以用来判断变...
In Python, None is a special constant that denotes the absence of value or a null value. It is object of its own datatype, the NoneType. 3. Using the is Operator The is operator is the most straightforward and recommended method to check if a variable is None. Using the is keyword ...
第一种是`if x is None`; 第二种是 `if not x:`; 第三种是`if not x is None`(这句这样理解更清晰`if not (x is None)`) 。 如果你觉得这样写没啥区别,那么你可就要小心了,这里面有一个坑。先来看一下代码: >>> x = 1 >>>notx ...
百度试题 结果1 题目在Python中,如何检查一个变量是否为空? A. if variable: B. if variable is not None: C. if variable == None: D. if variable != None: 相关知识点: 试题来源: 解析 a 反馈 收藏
if(len(third) == 0): print("Empty string") else: print("Not empty string") Yields below output. 3. Check String is Empty Using not Operator Thenotoperator is a logical operator that returnsTrueif the value or expression isFalse, andFalseif the value or expression isTrue. So if we ...
importosimportshutildefbackup_data(data,backup_path):ifdataisNoneordata==""ordata==[]:print("数据为空,无法备份")returnFalseelse:shutil.copy(data,backup_path)print(f"备份完成:{backup_path}")returnTruedata_file="example.txt"backup_location="/backup/example.txt"backup_data(data_file,backup_lo...
Typehelp()forinteractive help,orhelp(object)forhelp about object.>>>help()Welcome to Python3.6's help utility!Ifthisis your first time using Python,you should definitely check out the tutorial on the Internet at https://docs.python.org/3.6/tutorial/.Enter the nameofany module,keyword,or to...