On Wed, Feb 8, 2012 at 2:16 PM, janwillem <jwevand...@xs4all.nl> wrote:
> I would like to read a formula from text input and than process it
> further with sympy. I did not find a elegant solution for that. What
> works is the following work around using an intermediate script that
> is imported. I thought there might be a simpler and more elegant way.
> import sympy
> import string
> import re
> splits = '[\]\[ ()/*-=><^:]'
> #the formula that might come from text file or textbox of a gui
> f = 'fx = (x-2 * z)/f'
> lst = re.split(splits, f)
> #make temp script to be imported
> f_tmp = open('sympy_symbols.py', 'w')
> f_tmp.write('import sympy\n')
> for s in lst:
> if s != '' and s[0] in string.letters:
> f_tmp.write('%s = sympy.Symbol("%s")\n' % (s, s))
> f_tmp.write(f)
> f_tmp.close()
> #import temp script
> from sympy_symbols import *
> print fx
> dfdx = sympy.diff(fx, x)
> print dfdx
>
Although parsing of equations has not been implemented (though there
is a small script attached that does this at
http://code.google.com/p/sympy/issues/detail?id=2966 ) parsing of
expressions can be done with sympify() (alias S()):
>>> fx = S( ' (x-2 * z)/f ' )
>>> fx.diff(x)
1/f
If your expression has some other syntax (like that allowed in
Mathematica) there is a mathematica parser which is demonstrated in
the script of the issue cited above.
Let us know if you have more questions.
Chris
--
You received this message because you are subscribed to the Google Groups
"sympy" group.
To post to this group, send email to sympy@googlegroups.com.
To unsubscribe from this group, send email to
sympy+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/sympy?hl=en.
