Formatter error from sympy in ipython notebook

Question

I have the following Sympy related code in iPython Notebook:

from sympy import *
init_printing()

...

define constants

c, d, e, f = symbols("c, d, e, f")

...

define two matrices

v = Matrix(2,1,[1,1])
w = Matrix(2,1,[2,3])

define symbolic matrices

v, v1, v2 = symbols("v, v1, v2")
v = Matrix(2,1, [v1, v2])
w, w1, w2 = symbols("w, w1, w2")
w = Matrix(2,1, [w1, w2])

addition of symbolic vectors v & w

v + w

results in the following error message

/home/ron/anaconda/lib/python2.7/site-packages/IPython/core/formatters.py:239:  FormatterWarning: Exception in image/png formatter: 
\left[\begin{smallmatrix}v_{1} + w_{1}\\v_{2} + w_{2}\end{smallmatrix}\right]
      ^
Expected "\right" (at char 6), (line:1, col:7)
  FormatterWarning,

and then produces the correct answer

[v1+w1v2+w2]

The interesting thing is that if I re-execute the cell the error message goes away. I've tried the same code in ipython qtconsole with identical results. Is this a bug or just poor coding on my part?

After further searching I tried the following in the first cell:

from IPython.display import display

from sympy.interactive import printing
printing.init_printing(use_latex='mathjax')

from __future__ import division
import sympy as sym
from sympy import *

This eliminates the above errors so far.

New cell from SymPy: Open Source Symbolic Mathematics on nbviewer

Answer 1

This is a bug, which has been fixed in the git version of SymPy. You can safely ignore it. It will only be an issue if you export your notebook to a format that uses png for the math. If you want to suppress the error entirely, you can use init_printing(use_latex='mathjax').