def say_hi2(): print("你好呀") return None result = say_hi2() print(f"无返回值函数,返回的内容是:{result}") print(f"无返回值函数,返回的内容类型是:{type(result)}") # None用于if判断 def check_age(age): if age > 18: return "SUCCESS"
第二种方法是使用is关键字来判断一个值是否为None。None是Python中表示空值的特殊对象。我们可以使用is关键字来判断一个值是否等于None。下面是示例代码: defcheck_input(username,password):ifusernameisNone:print("用户名不能为空")ifpasswordisNone:print("密码不能为空")username=input("请输入用户名:")passwo...
def multi_permission_check(checks): def decorator(func): def wrapper(*args, **kwargs): for check in checks: if not check(*args, **kwargs): raise PermissionError("Permission check failed.") return func(*args, **kwargs) return wrapper return decorator def is_admin(user): return user.g...
foo =Noneiffoo is None: print("is None")iffoo ==None: print("also none") 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....
利用短路特性 ,可以优雅地实现条件赋值,无需显式使用if-else结构。例如,为变量赋予默认值: x = y or "default_value" 这段代码中,如果y是真值(非零、非空等) ,则x被赋予y的值;否则,x获得默认值"default_value"。 1.3 避免None错误的优雅方式
defcheck_user_exists(username):ifusername=="existing_user":return"用户名已存在"returnNone defregister_user(username,email,password):errors=[]errors.append(validate_username(username))errors.append(validate_email(email))errors.append(validate_password(password))errors.append(check_user_exists(username))...
modeldef evaluate_models(dataset, p_values, d_values, q_values):dataset = dataset.astype('float32')best_score, best_cfg = float("inf"), Nonefor p in p_values:for d in d_values:for q in q_values:order = (p,d,q)try:mse = evaluate_arima_model(dataset, order)if mse...
假设一个方块落地的逻辑已经实现if方块落地:# 将方块固定到网格上# ...# 检查是否有行被填满full_...
a=102content ="this is a very long string contains: %s, %s"%(string.ascii_lowercase, string.ascii_uppercase)ifnot(len(content)==0):if( (1+2) % (4+3) ) ==1andaisnotNone:pass 使用flake8 检查后得到的结果将会是这样: $ flake8 main.py ...
if isinstance(x, int): # Here type of x is int. x + 1 # OK else: # Here type of x is str. x + 'a' # OK f(1) # OK f('x') # OK f(1.1) # Error Note Optional 类型,可选类型, Optional[X] 相当于Union[X,None]: ...