How to substitute var by arrays?

Ronghai Wu

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Sep 21, 2015, 2:14:33 PM9/21/15

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Dear Sympy developers and users,

Could anyone help me with the following problem:
substitute a, b, c by arrays in expression f = a*b*c. For example, I get "ValueError: The truth value of an array with more than one element is ambiguous" if running:
import sympy
import numpy
sympy.var('a,b,c')
f = a*b*c
array1 = numpy.random.randint(1,3,3)
array2 = numpy.random.randint(1,3,3)
array3 = numpy.random.randint(1,3,3)
f.subs([[a, array1], [b, array2], [c, array3]])

Best Regards
Ronghai Wu

Aaron Meurer

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Sep 21, 2015, 2:16:20 PM9/21/15

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subs should only be used to replace sympy expressions with sympy
expressions. To evaluate a sympy expression at a numpy array, you
should lambdify() it first.

In [10]: f0 = lambdify((a, b, c), f)

In [12]: f0(array1, array2, array3)
Out[12]: array([2, 1, 1])

Aaron Meurer

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Ronghai Wu

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Sep 22, 2015, 4:34:52 AM9/22/15

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Hi Aaron Meurer,

Thanks, it works!

Ronghai

在 2015年9月21日星期一 UTC+2下午8:16:20，Aaron Meurer写道：

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