incorrect output when derivative respect to function, sometimes doit() give the corect answer, sometimes not

[chaowen guo]

  Hi:

  source code:

  import sympy
  x=sympy.symbols('x')
  y=sympy.exp(x)
  f=sympy.symbols('f',cls=sympy.Function)(y)
  import IPython.display
  IPython.display.Math(sympy.latex(f.diff(x,2)).replace('e^{x}','{e^{x}}'))#corrcet#replace is to work arround the latex output of e^{x}

  IPython.display.Math(sympy.latex(f.diff(x,2).doit()).replace('e^{x}','{e^{x}}'))#not corrcet#where is the leading 2 come from in the first term?

  IPython.display.Math(sympy.latex(f.diff(x).diff(x)).replace('e^{x}','{e^{x}}'))#correct

  IPython.display.Math(sympy.latex(f.diff(x).diff(x).doit()).replace('e^{x}','{e^{x}}'))#not correct#where is the leading 2 come from in the first term?

  IPython.display.Math(sympy.latex(f.diff(x).doit()).replace('e^{x}','{e^{x}}'))#correct

  IPython.display.Math(sympy.latex(f.diff(x).doit().diff(x)).replace('e^{x}','{e^{x}}'))#not correct#the df(xi)/d(xi) should not exist

  IPython.display.Math(sympy.latex(f.diff(y,2)).replace('e^{x}','{e^{x}}'))#not correct##where is the leading 2 come from?

  IPython.display.Math(sympy.latex(f.diff(y).doit().diff(y).doit()).replace('e^{x}','{e^{x}}'))#correct

output:



  Fom out [1] to out[6] show all the doit give incorrect answer, out[7] and out[8] show that doit give the correct answer. I want o ask whether it is a sympy bug or sympy has a special interpretation about such behavior?

[Aaron Meurer]

This looks like a bug. It's at least https://github.com/sympy/sympy/issues/7027, but there may be another bug there too.

Aaron Meurer

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[Riccardo Rossi]

Could this be the same as the problem I see here?

https://groups.google.com/forum/m/#!topic/sympy/ogz52F5Ol5c

Regards
Riccardo