Since empty strings areFalse,notoperator is used to check if the string is empty or not. Note that a string with only spaces is not considered empty, hence, you need to strip the spaces before checking for empty
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...
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...
not None == not False == not '' == not 0 == not [] == not {} == not () 但是,要注意区分不用not的情况: (p is q) 等价于 (id(p) == id(q))。 'if x is not None' 与 'if not x is None' 表达的含义是一致的。但建议用'if x is not None'。 'if not x is None' ...
The equality operator == is another way to check if variable is None in Python, but it is not recommended. Using the is keyword 1 2 3 4 5 x = None if(x == None): print("x is of the 'None' type.") Output: x is of the ‘None’ type. The == operator checks whether ...
python 直接if判断和is not None的区别 tmpName =''iftmpName:printtmpName#没有输出iftmpNameisnotNone:printtmpName#有输出,是空行
def get_input_int(s_mesg, fn_validate, default=None): while True: s = input(s_mesg).strip() if not s and default is not None: return default # not a default value; try it as an int try: n = int(s) except ValueError:
To check if a string is empty using the equality operator, we can just compare the string with another empty string. If the result is True, the input string is empty. Otherwise not. input_string="" print("The input string is:",input_string) ...
如果您的方法返回的值只有bool(returnValue)等于False,那么if not new:应该可以正常工作。这有时发生在内置libs中——例如,re.match返回none或truthy match对象。 也可以在这里看到我关于python中的null和None的答案。 So how can I question a variable that is a NoneType?