第一种方法是使用if语句来判断值是否为空。我们可以使用not关键字来判断一个值是否为None或空字符串。下面是示例代码: username=input("请输入用户名:")password=input("请输入密码:")ifnotusername:print("用户名不能为空")ifnotpassword:print("密码不能为空") 1. 2. 3. 4. 5. 6. 7. 8. 上述代码...
# unit test caseimportunittestclassTestMethods(unittest.TestCase):# test functiondeftest_negative(self):firstValue =None# error message in case if test case got failedmessage ="Test value is none."#assertIsNotNone() to check that if input value is not noneself.assertIsNotNone(firstValue, m...
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...
Using 'is' can be better when check is None or not, because 'is' is doing id comparsion: id(foo) == id(None) It is much faster check '==' it does a deep looking for the value.
None类型的应用场景 None作为一个特殊的字面量,用于表示:空,没有意义,有很多实际的应用场景。 用在函数无返回值上 用在if判断上 在if判断中None等于False 一般用于函数主动返回None,配合if做相关判断。 def check_age(age): if age>18: return "success" return None r=check_age(5) if not r: print("...
grid,grid_height,grid_width):full_rows=[]foryinrange(grid_height):ifall(grid[y][x]isnotNone...
1#使用__metaclass__(元类)的高级python用法2classSingleton2(type):3def__init__(cls,name,bases,dict):4super(Singleton2,cls).__init__(name,bases,dict)5cls._instance=None6def__call__(cls,*args,**kw):7ifcls._instance is None:8cls._instance=super(Singleton2,cls).__call__(*args,*...
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 ...
defcheck_hash(x):ifx.__hash__ is not None:printtype(x),'hashable:',hash(x)returnTrueelse:printtype(x),'unhashable'returnFalse # int i=5check_hash(i)# long l=sys.maxint+1check_hash(l)# float f=0.5check_hash(f)# string
) ==1andaisnotNone:pass 使用flake8 检查后得到的结果将会是这样: $ flake8 main.py main.py:1:1: F401'os'imported but unused main.py:4:2: E225 missing whitespace around operator main.py:6:58: E225 missing whitespace around operator ...