On Wed, Aug 8, 2012 at 2:02 PM, Matthew Rocklin <[email protected]> wrote:
> Would Piecewise work well here? > > > # Return 0 if x==0 else return log(x) > >>> monkey_log = Piecewise((0, Eq(x, 0)), (log(x), True)) > >>> fn = lambdify(x, monkey_log, 'mpmath') > >>> fn(0) > 0 > >>> fn(2.71828) > 0.999999327347282 > > Maybe I'm being dense, but I'm not sure I understand correctly what to do with this. How do I inject this into the namespace used for evaluating lam_func in the below? I want to replace the log function which is part of a bigger expression. Skipper > > > On Wed, Aug 8, 2012 at 11:37 AM, Skipper Seabold <[email protected]>wrote: > >> Hi, >> >> I'm trying to evaluate a Hessian that I'm computing symbolically. To do >> so, I'd like to monkey-patch the mpmath.log function to define log(0) == 0. >> I can replicate the error with the minimal example below. I get >> >> /usr/local/lib/python2.7/dist-packages/sympy/core/function.pyc in >> __new__(cls, *args, **options) >> >> 606 args = map(sympify, args) >> 607 result = super(AppliedUndef, cls).__new__(cls, *args, >> **options) >> --> 608 result.nargs = len(args) >> 609 return result >> 610 >> >> AttributeError: 'Float' object has no attribute 'nargs' >> >> >> However, what I'm seeing with my actual script is that the first time I >> run it, I get this error. The second time, it works, which is baffling. I >> am on recent sympy master from git. Anyone have any ideas? Am I doing this >> wrong? >> >> import sympy >> from sympy.abc import y,x,z >> from sympy.utilities.lambdify import implemented_function >> from sympy import Function >> from mpmath import mpf, log as mplog >> >> func_ = y * sympy.log(x) * z >> func = func_(y, x).subs({z : 2.0}) >> >> log = implemented_function(Function("log"), lambda x : mpf(0) if x == 0 >> else mplog(x)) >> >> lam_func = sympy.lambdify((y, x), func, [{'log' : log}, 'mpmath']) >> >> data = (1., 2.) >> lam_func(*data) >> >> Thanks, >> >> Skipper >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sympy" group. >> To post to this group, send email to [email protected]. >> To unsubscribe from this group, send email to >> [email protected]. >> For more options, visit this group at >> http://groups.google.com/group/sympy?hl=en. >> > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/sympy?hl=en. > -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
