You'll need to give more details on what your code is doing. The code
you posted works as expected. Both x == y and x is y should be False
because Symbols compare by name. It is possible the bug is in your own
code somewhere, as it would be difficult for y to "become" x exactly,
but it is also possible you stumbled on a bug in SymPy itself. Without
an example that reproduces the issue, it is impossible to say.
Aaron Meurer
On Wed, Jun 3, 2020 at 2:09 PM Jason Moore <moorepa...@gmail.com> wrote:
>
> Actually, I don't think your code is valid. You create two distinctly
> different symbols:
>
> In [1]: import sympy as sm
>
> In [2]: x = sm.Symbol('x')
>
> In [3]: y = sm.Symbol('y')
>
> In [4]: x == y
> Out[4]: False
>
> In [5]: x is y
> Out[5]: False
>
> In [6]: x + y
> Out[6]: x + y
>
> Jason
> moorepants.info
> +01 530-601-9791
>
>
> On Wed, Jun 3, 2020 at 1:06 PM Jason Moore <moorepa...@gmail.com> wrote:
>>
>> Yes, this is intentional. It is really no different than this:
>>
>> In [1]: a = 1
>>
>> In [2]: b = 1
>>
>> In [3]: type(a)
>> Out[3]: int
>>
>> In [4]: type(b)
>> Out[4]: int
>>
>> In [5]: a == b
>> Out[5]: True
>>
>> In [6]: a is b
>> Out[6]: True
>>
>> Jason
>> moorepants.info
>> +01 530-601-9791
>>
>>
>> On Wed, Jun 3, 2020 at 12:53 PM James Bateman <james.bate...@gmail.com>
>> wrote:
>>>
>>> I've just discovered a bug in my code which boiled down to the following,
>>> where a symbol "y" was given the same SymPy name as an existing symbol.
>>>
>>> import sympy as sp
>>> x = sp.Symbol('x')
>>> y = sp.Symbol('y')
>>>
>>> x == y # True
>>> x is y # True; expected False
>>> x + y # 2*x; expected x + x (which would have made the bug in my code more
>>> apparent)
>>>
>>> The behaviour here is very surprising to me. I would have expected x and y
>>> to be different Python objects with __repr__ methods which just so happen
>>> to return the same string. Instead, x and y are apparently different
>>> Python names for the same object (x is y).
>>>
>>> Is this intentional? I think I must misunderstand some deep design choice
>>> in SymPy, and I can't express my confusion well enough to Google it.
>>> Please help!
>>>
>>>
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