def myfunc(value=None): if value is None: value = [] # modify value here 1. 2. 3. 4. 如果你需要处理任意类型的数据(包括None在内),可以用一个哨兵实例: sentinel = object() def myfunc(value=sentinel): if value is sentinel: value = expression # use/modify value here 1. 2. 3. 4....
defmyfunc(value=None):ifvalueisNone:value=[]# modify value here 如果你需要处理任意类型的数据(包括None在内),可以用一个哨兵实例: sentinel=object()defmyfunc(value=sentinel):ifvalueissentinel:value=expression# use/modify value here 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...
value = []# modify value here 如果你需要处理任意类型的数据(包括None在内),可以用一个哨兵实例: python sentinel =object()defmyfunc(value=sentinel):ifvalueissentinel: value = expression# use/modify value here 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...
Python’s handling of default parameter values is one of a few things that tends to trip up most new Python programmers (but usually only once). What causes the confusion is the behaviour you get when you use a “mutable” object as a default value; that is, a value that can be modif...
"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. This is especially important to understand when a default parameter is...
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 ...
Return the “identity” of an object. This is an integer which is guaranteed to be unique and constant for this object during its lifetime. Two objects with non-overlapping lifetimes may have the same id() value. CPython implementation detail: This is the address of the object in memory....
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: ...
在python3.8之后函数参数中允许出现/和*号，/用来指明某些函数形参必须使用位置参数而非关键字参数的形式...
so It seems to me that the easiest thing would be that if the default value were a basic type (str, int, float, None), then it can stay, otherwise replace it with ... The more complex way to go about this would be to try the default value first, and if the AST reports a fail...