def function_name(parameter1, parameter2=default_value): # function body 复制代码 其中,parameter1 是必需参数,parameter2 是带有默认值的参数,default_value 是为该参数指定的默认值。 下面是一个示例: def greet(name, greeting='Hello'): print(greeting, name) # 调用函数时提供greeting参数的值 greet('...
Default parameter values arealwaysevaluated when, and only when, the “def” statement they belong to is executed; see: http://docs.python.org/ref/function.html(dead link) for the relevant section in the Language Reference. Also note that “def” is an executable statement in Python, and t...
def calculate(a, b, c, memo={}): try: value = memo[a, b, c] # return already calculated value except KeyError: value = heavy_calculation(a, b, c) memo[a, b, c] = value # update the memo dictionary return value 这种使用姿势在某些递归函数中非常有用(比如记忆化搜索)。 二是,对于...
importdatetimeasdtfromtimeimportsleepdeflog_time(msg, time =None):iftimeisNone: time = dt.datetime.now() sleep(1)print("%s: %s"% (time.isoformat(), msg)) log_time('msg 1') log_time('msg 2') log_time('msg 3') 详细介绍Python函数中的默认参数 Python:默认参数 Default Parameter Valu...
当且仅当默认参数所在的“def”语句执行的时候,默认参数才会进行计算。请看文档描述 https://docs.python.org/2/reference/compound_stmts.html#function-definitions 其中有下面一段 "Default parameter values are evaluated when the function definition is executed. This means that the expression is evaluated onc...
A. def function_name(parameter=None): B. def function_name(parameter): C. def function_name(parameter=default_value): D. def function_name(parameter, default_value): 相关知识点: 试题来源: 解析 C 【详解】 本题Python函数定义。在Python中,可以通过为参数指定默认值来使参数变为可选的。选项C ...
def function_name(parameter1, default_parameter=default_value): 函数体 关键字参数是在调用函数时,通过参数名指定参数值的方式,这可以让函数调用更加清晰易懂,同时也可以避免因参数顺序错误而导致的问题。 def function_name(parameter1, parameter2):
def myfunc(value=sentinel): if value is sentinel: value = expression # use/modify value here 1. 2. 3. 4. 5. 6. 当然在一些旧的代码里,object 还没有被引入 Python 的时候,下面语句也常被使用创建一个值为非假(not false)唯一实例:
Default parameter values are evaluated when the function definition is executed. This means that the expression is evaluated once, when the function is defined, and that the same “pre-computed” value is used for each call. 为了能够更好地理解文档内容,再来看一个例子: ...
Default parameter values are evaluated when the function definition is executed. This means that the expression is evaluated once, when the function is defined, and that the same “pre-computed” value is used for each call. 为了验证这句话,我们修改代码如下 def bad_append(new_item, a_list=[...