How to export expression in mathematica to python [closed]

Question

I have an expression in Mathematica; I want to convert this expression into python readable format. how to do this?

a=-4 b^16 Sin[(b^2 \[Gamma]^2)/Sqrt[\[Alpha]]]^2 (-4 b^2 Cos[b z1] Cos[b (L - z2)] Cos[
b (-z1 + z2)]^2)

Answer 1

You can use from sympy.parsing.mathematica import mathematica from python.

Copy the mathematica expression as string to Python and do the following

>python
Python 3.8.8 (default, Apr 13 2021, 19:58:26)
[GCC 7.3.0] :: Anaconda, Inc. on linux
>>> from sympy.parsing.mathematica import mathematica
>>> from sympy import var
>>> b,Gamma,L,Alpha,z1,z2 = var('a Gamma L Alpha z1 z2')
>>> expr='16 b^18 Cos[b z1] Cos[b (L - z2)] Cos[b (-z1 + z2)]^2 Sin[(b^2 Gamma^2)/Sqrt[Alpha]]^2'
>>> my_expr_in_python  = mathematica(expr)
>>> my_expr_in_python

Gives

16*b**18*sin(Gamma**2*b**2/sqrt(Alpha))**2*cos(b*z1)*cos(b*(L - z2))*cos(b*(-z1 + z2))**2

Note that the parser in Python does not handle '\[Gamma]' and '\[Alpha]' as they are inside Mathematica. These have to be done using normal non-Greek text in Mathematica and avoid using the palettes symbols.

Every symbol needs to be defined in sympy using the var command. For example to convert Sin[x] Log[y] then do

>>> x,y = var('x y')
>>> expr='Sin[x] Log[y]'
>>> mathematica(expr)

log(y)*sin(x)

You can read more about Python's Mathematica parser and how to use it on https://docs.sympy.org/latest/modules/parsing.html

You can also add your own side translations of Mathematica expressions if you want, as shown in the example on the above page.

Answer 2

Does this ad-hoc transformation work?

ClearAll[a, b, \[Alpha], \[Gamma]]
 
eq = a == -4 b^16 Sin[(b^2 \[Gamma]^2)/Sqrt[\[Alpha]]]^2 (-4 b^2 Cos[
       b z1] Cos[b (L - z2)] Cos[b (-z1 + z2)]^2);

StringReplace[
 ToString@CForm[eq], {"Power" -> "pow", "Sin" -> "sin", 
  "Cos" -> "cos", "Sqrt" -> "sqrt", "\[Alpha]" -> "alpha", 
  "\[Gamma]" -> "gamma"}]

(* "a == 16*pow(b,18)*cos(b*z1)*cos(b*(L - z2))*pow(cos(b*(-z1 \
+ z2)),2)*pow(sin((pow(b,2)*pow(gamma,2))/sqrt(alpha)),2)" *)
```