"""Check for errs in the AST. The Python parser does not catch all syntax errors.  Others, likeassignments with invalid targets, are caught in the code generationphase. The compiler package catches some errors in the transformer module.But it seems clearer to write checkers that use the AST to detecterrors.""" from compiler import ast, walk def check(tree, multi=None):    v = SyntaxErrorChecker(multi)    walk(tree, v)    return v.errors class SyntaxErrorChecker:    """A visitor to find syntax errors in the AST."""     def __init__(self, multi=None):        """Create new visitor object.         If optional argument multi is not None, then print messages        for each error rather than raising a SyntaxError for the        first.        """        self.multi = multi        self.errors = 0     def error(self, node, msg):        self.errors = self.errors + 1        if self.multi is not None:            print "%s:%s: %s" % (node.filename, node.lineno, msg)        else:            raise SyntaxError, "%s (%s:%s)" % (msg, node.filename, node.lineno)     def visitAssign(self, node):        # the transformer module handles many of these        pass##        for target in node.nodes:##            if isinstance(target, ast.AssList):##                if target.lineno is None:##                    target.lineno = node.lineno##                self.error(target, "can't assign to list comprehension")