Currently there is not, but I don't think it would be very difficult
to add the behavior in as a global parameter at least. If you want to
just make it an option to sympify (like sympify('1 + 1',
evaluate=False)), I don't know how difficult that would be, since the
parser would have to be modified, but it should be doable. But we
definitely would accept a patch that does so. Please open an issue for
it in any case.
As for multiplying by something causing an unevaluated expression to
evaluate, I consider this to be a bug. It no longer does it in master
with 1 (because the constructor ignores the identity), but it will
still do it with any other number.
Aaron Meurer
On Sun, Oct 2, 2011 at 10:44 PM, gsagrawal <[email protected]> wrote:
> yes , i am facing the same problems.
> specially when you try to convert a string format user input into a valid
> sympy expression using simpify(expr) which internally calls Add and Mul with
> default parameter (evaluate=true). is there any way to control this ?
> On Mon, Oct 3, 2011 at 2:44 AM, Gabor Takacs <[email protected]> wrote:
>>
>> Hi,
>>
>> I experienced that sympy applies automatic evaluation at expression
>> creation by default
>> (the evaluate parameter is True in the constructors).
>>
>> Therefore, e.g.
>> - I**3 evaluates to -I
>> - Pow(I, 3, evaluate=False) evaluates to I**3, but
>> Pow(I, 3, evaluate=False) * 1 evaluates to -I
>>
>> Is it possible to change the default behaviour to "no automatic
>> evaluation at expression creation"?
>> (so that I**3 evaluates to I**3)
>>
>> Gabor
>>
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