[Tutor] Why is it invalid syntax to have a particular dictionary value as an argument?

[Emile van Sebille]

On 4/6/2015 12:42 PM, Dave Angel wrote:
> On 04/06/2015 03:20 PM, Emile van Sebille wrote:
<snip>
>> Python 2.7.6 (default, Mar 22 2014, 22:59:56)
>> [GCC 4.8.2] on linux2
>> Type "help", "copyright", "credits" or "license" for more information.
>>  >>> d = {'a':'123'}
>>  >>> def func(s=d['a']):
>> ...   print s
>> ...
>>  >>> func()
>> 123
>>
>
> Only if you know that nobody is going to be changing d.

Clearly my example avoids the pitfalls of a changing d.  :)

>  >>> d = {"a":"123"}
>  >>> def func(s=d["a"]):
> ...     print s
> ...
>  >>> d["a"] = "new value"
>  >>> func()
> 123

Good point -- I forgot about setting default parameters at compile time.

 >>> d={'a':'123'}
 >>> def func(s=d):print s['a']
...
 >>> func()
123
 >>>
 >>> d['a']='456'
 >>> func()
456
 >>>