smpy real to mpf?

[Zoho]

Hello:

I would like convert a sympy real to an mpf. Is this possible? I am on
Debian sid with the latest packages.

In [1]: import sympy as syp

In [2]: import mpmath as mp

In [3]: x = syp.symbols('x')

In [4]: a = syp.diff(syp.exp(1.0/4*x**2), x, 2).subs('x', 0)

In [5]: type(a)
Out[5]: <class 'sympy.core.numbers.Real'>

In [6]: a = syp.diff(syp.exp(1.0/4*x**2), x, 2).subs('x', 0).evalf()

In [7]: type(a)
Out[7]: <class 'sympy.core.numbers.Real'>

In [8]: a = float(syp.diff(syp.exp(1.0/4*x**2), x, 2).subs('x', 0))

In [9]: type(a)
Out[9]: <type 'float'>

In [10]: a = mp.mpf(syp.diff(syp.exp(1.0/4*x**2), x, 2).subs('x', 0))
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)

/home/brent/<ipython console> in <module>()

/var/lib/python-support/python2.5/mpmath/mptypes.py in __new__(cls,
val)
242 raise ValueError
243 else:
--> 244 return make_mpf(fpos(mpf_convert_arg(val), gp,
gr))
245
246 man_exp = property(lambda self: self._mpf_[1:3])

/var/lib/python-support/python2.5/mpmath/mptypes.py in
mpf_convert_arg(x)
201 if isinstance(x, basestring): return from_str(x, gp, gr)
202 if hasattr(x, '_mpf_'): return x._mpf_
--> 203 raise TypeError("cannot create mpf from " + repr(x))
204
205 def mpf_convert_rhs(x):

TypeError: cannot create mpf from 0.5

[Ondrej Certik]

Fredrik is supposed to fix these things as part of his GSoC, in the
meantime, use this:

In [1]: a = diff(exp(x**2/4), x, 2).subs(x, 0)

In [2]: from sympy.thirdparty.mpmath import mpf

In [3]: mpf(float(a))
Out[3]: 0.5

Ondrej