Reorder functions in linexprs.py

[linpy.git] / linpy / linexprs.py

diff --git a/linpy/linexprs.py b/linpy/linexprs.py
index 82d75d0..fce77a6 100644 (file)
--- a/linpy/linexprs.py
+++ b/linpy/linexprs.py
@@ -348,7 +348,10 @@ class LinExpr:
         # add implicit multiplication operators, e.g. '5x' -> '5*x'
         string = LinExpr._RE_NUM_VAR.sub(r'\1*\2', string)
         tree = ast.parse(string, 'eval')
-        return cls._fromast(tree)
+        expr = cls._fromast(tree)
+        if not isinstance(expr, cls):
+            raise SyntaxError('invalid syntax')
+        return expr
 
     def __repr__(self):
         string = ''
@@ -453,8 +456,13 @@ class Symbol(LinExpr):
         """
         if not isinstance(name, str):
             raise TypeError('name must be a string')
+        node = ast.parse(name)
+        try:
+            name = node.body[0].value.id
+        except (AttributeError, SyntaxError):
+            raise SyntaxError('invalid syntax')
         self = object().__new__(cls)
-        self._name = name.strip()
+        self._name = name
         self._coefficients = {self: Fraction(1)}
         self._constant = Fraction(0)
         self._symbols = (self,)
@@ -493,16 +501,6 @@ class Symbol(LinExpr):
         """
         return Dummy(self.name)
 
-    @classmethod
-    def _fromast(cls, node):
-        if isinstance(node, ast.Module) and len(node.body) == 1:
-            return cls._fromast(node.body[0])
-        elif isinstance(node, ast.Expr):
-            return cls._fromast(node.value)
-        elif isinstance(node, ast.Name):
-            return Symbol(node.id)
-        raise SyntaxError('invalid syntax')
-
     def __repr__(self):
         return self.name
 
@@ -520,6 +518,21 @@ class Symbol(LinExpr):
             raise TypeError('expr must be a sympy.Symbol instance')
 
 
+def symbols(names):
+    """
+    This function returns a tuple of symbols whose names are taken from a comma
+    or whitespace delimited string, or a sequence of strings. It is useful to
+    define several symbols at once.
+
+    >>> x, y = symbols('x y')
+    >>> x, y = symbols('x, y')
+    >>> x, y = symbols(['x', 'y'])
+    """
+    if isinstance(names, str):
+        names = names.replace(',', ' ').split()
+    return tuple(Symbol(name) for name in names)
+
+
 class Dummy(Symbol):
     """
     A variation of Symbol in which all symbols are unique and identified by
@@ -573,21 +586,6 @@ class Dummy(Symbol):
         return '$${}_{{{}}}$$'.format(self.name, self._index)
 
 
-def symbols(names):
-    """
-    This function returns a tuple of symbols whose names are taken from a comma
-    or whitespace delimited string, or a sequence of strings. It is useful to
-    define several symbols at once.
-
-    >>> x, y = symbols('x y')
-    >>> x, y = symbols('x, y')
-    >>> x, y = symbols(['x', 'y'])
-    """
-    if isinstance(names, str):
-        names = names.replace(',', ' ').split()
-    return tuple(Symbol(name) for name in names)
-
-
 class Rational(LinExpr, Fraction):
     """
     A particular case of linear expressions are rational values, i.e. linear