Status: New
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 2545 by [email protected]: lambdify expression containing pi
http://code.google.com/p/sympy/issues/detail?id=2545
Lambdify of expressions that contain for example a pi
does not work as expected. Here is a small example:
# Create an expression
x = sympy.Symbol("x")
y = x**2 + sympy.pi
# lamdbfiy and specify "numpy" as we want to do numerics
# and are *only* interersted in floating point numbers later
f = sympy.lambdify(x, y, "numpy")
# Test:
In [9]: f(2)
Out[9]: pi + 4
# Hmm, suspicious "pi" here
# Oh and the type is something really not suitable
# for further numerical computations ...
In [11]: type(f(2))
Out[11]: <class 'sympy.core.add.Add'>
# Let's test with a numpy array as input
In [13]: u = numpy.linspace(-2,2,10)
In [14]: f(u)
Out[14]:
array([pi + 4.0, 2.41975308641975 + pi, 1.23456790123457 + pi,
0.444444444444445 + pi, 0.0493827160493828 + pi,
0.0493827160493828 + pi, 0.444444444444444 + pi,
1.23456790123457 + pi, 2.41975308641975 + pi, pi + 4.0],
dtype=object)
# It get's even worse! We would like to have a
# dtype of float or something linke that but not "object" arrays.
# At least the type f(u) is a ndarray
In [15]: type(f(u))
Out[15]: <type 'numpy.ndarray'>
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