thanks for your kind help ,but there is no '*' in x Sin[1/x] + Abs[x] 在 2014年11月23日星期日UTC+8上午12时13分22秒，Ondřej Čertík写道： > > Hi Lee, > > On Sat, Nov 22, 2014 at 4:04 AM, Lee Philip <[email protected] > <javascript:>> wrote: > > is 'x sin(1/x)+abs(x)' or 'x sin(1/x)+|x|' or 'x Sin[1/x] + Abs[x]' > sympy > > acceptable? > > > > I got exceptions by these expressions ,wonder is this a bug or not ? > > You seem to found a bug in the Mathematica parser, i.e. this works: > > In [7]: M("x*Sin[x]") > Out[7]: x⋅sin(x) > > In [9]: M("Sin[1/x]") > Out[9]: > ⎛1⎞ > sin⎜─⎟ > ⎝x⎠ > > But this fails: > > In [10]: M("x*Sin[1/x]") > --------------------------------------------------------------------------- > > TypeError Traceback (most recent call > last) > <ipython-input-10-e58ebb4f8e06> in <module>() > ----> 1 M("x*Sin[1/x]") > > /home/ondrej/repos/sympy/sympy/parsing/mathematica.py in mathematica(s) > 6 > 7 def mathematica(s): > ----> 8 return sympify(parse(s)) > 9 > 10 > > /home/ondrej/repos/sympy/sympy/core/sympify.pyc in sympify(a, locals, > convert_xor, strict, rational, evaluate) > 315 try: > 316 a = a.replace('\n', '') > --> 317 expr = parse_expr(a, local_dict=locals, > transformations=transformations, evaluate=evaluate) > 318 except (TokenError, SyntaxError) as exc: > 319 raise SympifyError('could not parse %r' % a, exc) > > /home/ondrej/repos/sympy/sympy/parsing/sympy_parser.pyc in > parse_expr(s, local_dict, transformations, global_dict, evaluate) > 818 code = compile(evaluateFalse(code), '<string>', 'eval') > 819 > --> 820 return eval_expr(code, local_dict, global_dict) > 821 > 822 > > /home/ondrej/repos/sympy/sympy/parsing/sympy_parser.pyc in > eval_expr(code, local_dict, global_dict) > 731 """ > 732 expr = eval( > --> 733 code, global_dict, local_dict) # take local objects > in preference > 734 > 735 return expr > > <string> in <module>() > > TypeError: 'Symbol' object has no attribute '__getitem__' > > > I reported it here: > > https://github.com/sympy/sympy/issues/8501 > > However, if you just want to use sympy, don't use the Mathematica > parser, but rather sympy directly, like this: > > In [11]: var("x") > Out[11]: x > > In [12]: x*sin(1/x)+abs(x) > Out[12]: > ⎛1⎞ > x⋅sin⎜─⎟ + │x│ > ⎝x⎠ > > In [13]: _.diff(x) > Out[13]: > d d ⎛1⎞ > re(x)⋅──(re(x)) + im(x)⋅──(im(x)) cos⎜─⎟ > dx dx ⎛1⎞ ⎝x⎠ > ───────────────────────────────── + sin⎜─⎟ - ────── > │x│ ⎝x⎠ x > > Ondrej > > > > > > > > > test code here > > > > http://codepad.org/NyO5tj1I > > > > -- > > You received this message because you are subscribed to the Google > Groups > > "sympy" group. > > To unsubscribe from this group and stop receiving emails from it, send > an > > email to [email protected] <javascript:>. > > To post to this group, send email to [email protected] > <javascript:>. > > Visit this group at http://groups.google.com/group/sympy. > > To view this discussion on the web visit > > > https://groups.google.com/d/msgid/sympy/988b0ad3-bb8d-4ba6-9509-ad395f4353d2%40googlegroups.com. > > > > For more options, visit https://groups.google.com/d/optout. >
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