How do I construct this rational expression?

[Joachim Durchholz]

I need to update a unit test where integrate now returns something that
contains 1/(2*(s+1)).
However, when I write that subexpression, SymPy gives me 1/(2*s + 2),
which compares unequal.

What would be the best way forward?
Alternatives that I can think of:
- have integrate() do whatever SymPy does when constructing 1/(2*s + 2)
- have the unit test do it and leave integrate() as it is
- rewrite the unit test to directly construct the Expr object (how?)

[James Crist]

One way that's pretty common is to do something like:

result = whatever your testing
solution = something you type in
assert simplify(result - solution) == 0

This is better than constructing a special case form, because that form may change in the future.

[Aaron Meurer]

Except in the tests you should use a more directed, efficient
simplification function than simplify(). cancel() should be sufficient
for this case.

Aaron Meurer

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[Joachim Durchholz]

Am 28.03.2015 um 21:35 schrieb Aaron Meurer:
> Except in the tests you should use a more directed, efficient
> simplification function than simplify(). cancel() should be sufficient
> for this case.

That worked, thanks.

Is there a guideline which function to select for what kind of
normalization?
(I admit I haven't read SymPy's documentation, reading it all has always
been a daunting task.)