On Sat, 14 Apr 2007 17:33:11 -0800, Troy Melhase wrote:
> On 4/14/07, Mike <[EMAIL PROTECTED]> wrote:
>> While trying to write a recursive function involving lists, I came
>> across some (to me) odd behavior which I don't quite understand. Here's
>> a trivial function showing the problem.
>
> from http://docs.python.org/ref/function.html :
>
> 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 that same ``pre-computed'' value is used
> for each call. This is especially important to understand when a
> default parameter is a mutable object, such as a list or a dictionary:
> if the function modifies the object (e.g. by appending an item to a
> list), the default value is in effect modified.
This comes up so often that I wonder whether Python should issue a warning
when it sees [] or {} as a default argument.
What do people think? A misuse or good use of warnings?
--
Steven.
--
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