Perhaps the use() function can do what you want. Here's the docstring:
use(expr, func, level=0, args=(), kwargs={})
Use ``func`` to transform ``expr`` at the given level.
Example
=======
>>> from sympy import use, expand
>>> from sympy.abc import x, y
>>> f = (x + y)**2*x + 1
>>> use(f, expand, level=2)
x*(x**2 + 2*x*y + y**2) + 1
>>> expand(f)
x**3 + 2*x**2*y + x*y**2 + 1
By the way, if you are using this to map integrate() across an Add,
might I suggest that this is a bad idea. It turns out that you cannot
just do this, like you can with derivatives. The reason is that you
can have a sum for which each term it does not have an expressible
integral, but the whole sum does. For example, Integral(x**x, x) and
Integral(x**x*log(x), x) are both nonelementary functions, but
Integral(x**x + x**x*log(x), x) is an elementary function, as it's
equal to x**x.
Aaron Meurer
On Wed, Aug 10, 2011 at 3:42 PM, Chris Smith <smi...@gmail.com> wrote:
> On Thu, Aug 11, 2011 at 12:40 AM, Roberto Colistete Jr.
> <roberto.colist...@gmail.com> wrote:
>> Hi,
>>
>> I have not found a simple way to map a function to a mathematical
>> expression with sum of items. Is there anything simple to do it ? I
>> was thinking it would be simples, like "map(expand,expr)" but it
>> doesn't work.
>>
>> In the meantime, I have solved this issue with the code :
>>
>> def mapexpr(self,expr,func):
>> if isinstance(expr,Add):
>> return apply(Add,map(func,expr.args))
>> else:
>> return func(expr)
>>
>
> It sounds like you want to apply the function term-wise. What you have
> written above can be simplified to
>
> def map_termwise(func, expr):
> return Add(*[func(a) for a in Add.make_args(expr)])
>
> There is also a Mul.make_args. Both Add and Mul make_args methods
> interpret the expr as an Add or Mul, respectively.
>
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