Is there a complete example to write a mathematical expression in sympy to a Microsoft Word document?

This works for me:

from sympy import *
from docx import Document
from lxml import etree

# create expression
x, y = symbols('x y')
expr1 = (x+y)**2

# create MathML structure
expr1xml = mathml(expr1, printer = 'presentation')
tree = etree.fromstring('<math xmlns="http://www.w3.org/1998/Math/MathML">'+expr1xml+'</math>')

# convert to MS Office structure
xslt = etree.parse('C:/MML2OMML.XSL')
transform = etree.XSLT(xslt)
new_dom = transform(tree)

# write to docx
document = Document()
p = document.add_paragraph()
p._element.append(new_dom.getroot())
document.save("simpleEq.docx")

How about the following. The capture captures whatever is printed. In this case I use pprint to print the expression that I want written to file. There are lots of options you can use with pprint (including wrapping which you might want to set to False). The quality of output will depend on the fonts you use. I don't do this at all so I don't have a lot of hints for that.

from pprint import pprint
from sympy.utilities.iterables import capture
from sympy.abc import x
from sympy import Integral
with open('out.doc','w',encoding='utf-8') as f:
    f.write(capture(lambda:pprint(Integral(x**2, (x, 1, 3)))))

When I double click (in Windows) on the out.doc file, a word equation with the integral appears.

Here is the actual IPython session:

IPython console for SymPy 1.6.dev (Python 3.7.3-32-bit) (ground types: python)

These commands were executed:
>>> from __future__ import division
>>> from sympy import *
>>> x, y, z, t = symbols('x y z t')
>>> k, m, n = symbols('k m n', integer=True)
>>> f, g, h = symbols('f g h', cls=Function)
>>> init_printing()

Documentation can be found at https://docs.sympy.org/dev


In [1]: pprint(Integral(x**2, (x, 1, 3)))
3
(
?  2
? x  dx
)
1

In [2]: from pprint import pprint
   ...: from sympy.utilities.iterables import capture
   ...: from sympy.abc import x
   ...: from sympy import Integral
   ...: with open('out.doc','w',encoding='utf-8') as f:
   ...:     f.write(capture(lambda:pprint(Integral(x**2, (x, 1, 3)))))
   ...:

{problems pasting the unicode here, but it shows up as an integral symbol in console}