Allow leading underscores in symbols in LinExpr.fromstring()

diff --git a/linpy/linexprs.py b/linpy/linexprs.py
index b5864e1..b97f048 100644 (file)
--- a/linpy/linexprs.py
+++ b/linpy/linexprs.py
@@ -331,7 +331,7 @@ class LinExpr:
                 return left / right
         raise SyntaxError('invalid syntax')
 
-    _RE_NUM_VAR = re.compile(r'(\d+|\))\s*([^\W\d_]\w*|\()')
+    _RE_NUM_VAR = re.compile(r'(\d+|\))\s*([^\W\d]\w*|\()')
 
     @classmethod
     def fromstring(cls, string):