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...
栽在Python 的默认参数的“坑”中几次之后打算专门弄一篇博客来说一下这个事情。但是最近看到一篇很好地英文文章(Default Parameter Values in Python,Fredrik Lundh | July 17, 2008 | based on a comp.lang.python post),鞭辟入里。珠玉在前,就不舞文弄墨了。当然,也算是偷个懒,在这里简单翻译一下,希望更...
引子 栽在Python 的默认参数的“坑”中几次之后打算专门弄一篇博客来说一下这个事情。但是最近看到一篇很好地英文文章(Default Parameter Values in Python,Fredrik Lundh | July 17, 2008 | based on a comp.lang.python post),鞭辟入里。珠玉在前,就不舞文弄墨了。当然,也算是偷个懒,在这里简单翻译一下,...
l.append(value)returnlprint(foo("a"))print(foo("b", []))print(foo("c"))""" ['a'] ['b'] ['c'] """ that's all, see also: Python函数默认参数陷阱,你知道吗?|Default Parameter Values in Python|函数的默认参数陷阱
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 ...
"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...
If you’ve called it with arguments, then _func will be None, and some of the keyword arguments may have been changed from their default values. The asterisk in the argument list means that you can’t call the remaining arguments as positional arguments. Line 6: In this case, you called...
def functionName(parameter1,parameter2): suite 2、一些相关的概念 def是一个可执行语句 因此可以出现在任何能够使用语句的地方,甚至可以嵌套于其它语句中,例如if或while中 def创建了一个对象并将其赋值给一个变量名(即函数名上面语法中的functionName) return用于返回结果对象,其为可选,无return语句的函数,自动...
在以下示例中,通过接受统计类型 (GPString) 的字段名称和字符串值的两列来定义值表参数。通过使用ValueList过滤器和一组值,会在相应的GPValueTable列下生成下拉列表。要为值表参数设置默认值,可使用values属性并在值列表中提供参数值。 defgetParameterInfo(self):param0=arcpy.Parameter(displayName='Input Features...