Here's my solution for a customized sort key. Does this seem reasonable?
I just copied the format for the sort key for numbers and applied it to
anything that was real. It seems to work how I'd want it to work.
def customized_sort_key(item, order=None):
try:
x=sympify(item)
except:
pass
else:
if x.is_real:
return ((1, 0, 'Number'), (0, ()), (), x)
return default_sort_key(item,order)
On Saturday, October 18, 2014 8:52:50 PM UTC-5, Duane Nykamp wrote:
>
> I was using sympy's default_sort_order to sort objects. However, I
> realized that it does not sort numerical quantities in order:
>
> In [15]: sorted([-1, -1-sqrt(2),1+sqrt(2), pi, 4], key=default_sort_key)
> Out[15]: [-1, 4, pi, 1 + sqrt(2), -sqrt(2) - 1]
>
> The default sort key, lex, works in this case
>
> In [16]: sorted([-1, -1-sqrt(2),1+sqrt(2), pi, 4])
> Out[16]: [-sqrt(2) - 1, -1, 1 + sqrt(2), pi, 4]
>
> but that doesn't work on symbolic objects.
>
> Is there a way to sort that works on all sympy objects, symbolic or not,
> but still produces the normal order for numerical quantities?
>
> The only thing I can think of is trying the lex sort key first, then
> reverting to default_sort_key on TypeError. But, that has the undesirable
> effect of changing the relative order of numerical quantities once a
> symbolic quantity is added to the mix.
>
> Any suggestions or pointers to a place where this is discussed already?
>
> Thanks,
> Duane
>
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