Strip spaces after first $ for math equations. Required to produce single-$ math equations when running IPython nbconvert --to=latex

gistfile1.py

from IPython.nbconvert.preprocessors import *
import re


class StripDollarSpacesPreprocessor(Preprocessor):
    """Remove spaces after leading '$' in math equations.
    
    Make sure '$ a=10 $' is converted to '$a=10 $' and not '\$ a=10 \$' 
    when running nbconvert and pandoc
    """

    def replfunc(self,match):
        """ Match '$<space>' and replace by single '$' """
        x = '\$(\s+)'
        regex2 = re.compile(x)
        a= match.group(0)
        return regex2.sub('$',a)

    def preprocess_cell(self, cell, resources, index):
        """Find all '$' delimited equations and strip space after starting '$'
        """
        stringmatch = r'([\$\'])(?:(?=(\\?))\2.)*?\1'
        regex = re.compile(stringmatch)
        
        if 'source' in cell and cell.cell_type == "markdown":
            cell.source =  regex.sub(self.replfunc,cell.source)
        return cell, resources