Hi Colin,
The problem with 'S' is that it is a singleton factory:
In [8]: sympify('S.Zero')
Out[8]: 0
In [9]: sympify('S.One')
Out[9]: 1
So sympify('S*x') can't work:
In [10]: sympify('S')
Out[10]: S
In [11]: type(_)
Out[11]: <type 'instance'>
For the similar reason sympify('lambda') does not work:
In [13]: sympify('lambda x: x')
Out[13]: Lambda(x, x)
In [14]: sympify('lambda')
SympifyError: Sympify of expression 'lambda' failed, because of
exception being raised:
SyntaxError: unexpected EOF while parsing (line 1)
Our parser should be more intelligent in those cases.
Mateusz
2008/4/1, Colin Gillespie <[EMAIL PROTECTED]>:
>
> I've just found out that it's not 'E' that's causing the problem, it's
> 'S'.
>
> sympify('S') #works
> sympify('S*X') #doesn't work
>
> Cheers
>
>
> Colin
>
>
> On Mar 31, 5:29 pm, Colin Gillespie <[EMAIL PROTECTED]> wrote:
> > Dear All,
> >
> > I suspect that sympify is getting confused by python's builtin lambda
> > and E
> >
> > So are the following examples bugs? If not, should the documentation
> > be updated with a warning?
> >
> > >>> sympify('S*lambda')
> >
> > Traceback (most recent call last):
> > File "<stdin>", line 1, in ?
> > File "/pythonModules/lib/python2.4/site-packages/sympy-0.5.13_hg-
> > py2.4.egg/sympy/core/sympify.py", line 127, in sympify
> > raise SympifyError(a, exc)
> > sympy.core.sympify.SympifyError: Sympify of expression 'S*lambda'
> > failed, because of exception being raised:
> > SyntaxError: unexpected EOF while parsing (line 1)
> >
> > and
> >
> > >>> sympify('S*E')
> >
> > Traceback (most recent call last):
> > File "<stdin>", line 1, in ?
> > File "/data/ncsg3/pythonModules/lib/python2.4/site-packages/
> > sympy-0.5.13_hg-py 2.4.egg/sympy/core/sympify.py", line 127, in
> > sympify
> > raise SympifyError(a, exc)
> > sympy.core.sympify.SympifyError: Sympify of expression 'S*E' failed,
> > because of exception being raised:
> > TypeError: unsupported operand type(s) for *: 'instance' and 'Exp1'
> >
> > Cheers
> >
> > Colin
> >
>
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