"""Generate ast module from specification This script generates the ast module from a simple specification,which makes it easy to accomodate changes in the grammar.  Thisapproach would be quite reasonable if the grammar changed often.Instead, it is rather complex to generate the appropriate code.  Andthe Node interface has changed more often than the grammar.""" import fileinputimport getoptimport reimport sysfrom StringIO import StringIO SPEC = "ast.txt"COMMA = ", " def load_boilerplate(file):    f = open(file)    buf = f.read()    f.close()    i = buf.find('### ''PROLOGUE')    j = buf.find('### ''EPILOGUE')    pro = buf[i+12:j].strip()    epi = buf[j+12:].strip()    return pro, epi def strip_default(arg):    """Return the argname from an 'arg = default' string"""    i = arg.find('=')    if i == -1:        return arg    t = arg[:i].strip()    return t P_NODE = 1P_OTHER = 2P_NESTED = 3P_NONE = 4 class NodeInfo:    """Each instance describes a specific AST node"""    def __init__(self, name, args):        self.name = name        self.args = args.strip()        self.argnames = self.get_argnames()        self.argprops = self.get_argprops()        self.nargs = len(self.argnames)        self.init = []     def get_argnames(self):        if '(' in self.args:            i = self.args.find('(')            j = self.args.rfind(')')            args = self.args[i+1:j]        else:            args = self.args        return [strip_default(arg.strip())                for arg in args.split(',') if arg]     def get_argprops(self):        """Each argument can have a property like '*' or '!'         XXX This method modifies the argnames in place!        """        d = {}        hardest_arg = P_NODE        for i in range(len(self.argnames)):            arg = self.argnames[i]            if arg.endswith('*'):                arg = self.argnames[i] = arg[:-1]                d[arg] = P_OTHER                hardest_arg = max(hardest_arg, P_OTHER)            elif arg.endswith('!'):                arg = self.argnames[i] = arg[:-1]                d[arg] = P_NESTED                hardest_arg = max(hardest_arg, P_NESTED)            elif arg.endswith('&'):                arg = self.argnames[i] = arg[:-1]                d[arg] = P_NONE                hardest_arg = max(hardest_arg, P_NONE)            else:                d[arg] = P_NODE        self.hardest_arg = hardest_arg         if hardest_arg > P_NODE:            self.args = self.args.replace('*', '')            self.args = self.args.replace('!', '')            self.args = self.args.replace('&', '')         return d     def gen_source(self):        buf = StringIO()        print >> buf, "class %s(Node):" % self.name        self._gen_init(buf)        print >> buf        self._gen_getChildren(buf)        print >> buf        self._gen_getChildNodes(buf)        print >> buf        self._gen_repr(buf)        buf.seek(0, 0)        return buf.read()     def _gen_init(self, buf):        if self.args:            print >> buf, "    def __init__(self, %s, lineno=None):" % self.args        else:            print >> buf, "    def __init__(self, lineno=None):"        if self.argnames:            for name in self.argnames:                print >> buf, "        self.%s = %s" % (name, name)        print >> buf, "        self.lineno = lineno"        # Copy the lines in self.init, indented four spaces.  The rstrip()        # business is to get rid of the four spaces if line happens to be        # empty, so that reindent.py is happy with the output.        for line in self.init:            print >> buf, ("    " + line).rstrip()     def _gen_getChildren(self, buf):        print >> buf, "    def getChildren(self):"        if len(self.argnames) == 0:            print >> buf, "        return ()"        else:            if self.hardest_arg < P_NESTED:                clist = COMMA.join(["self.%s" % c                                    for c in self.argnames])                if self.nargs == 1:                    print >> buf, "        return %s," % clist                else:                    print >> buf, "        return %s" % clist            else:                if len(self.argnames) == 1:                    print >> buf, "        return tuple(flatten(self.%s))" % self.argnames[0]                else:                    print >> buf, "        children = []"                    template = "        children.%s(%sself.%s%s)"                    for name in self.argnames:                        if self.argprops[name] == P_NESTED:                            print >> buf, template % ("extend", "flatten(",                                                      name, ")")                        else:                            print >> buf, template % ("append", "", name, "")                    print >> buf, "        return tuple(children)"     def _gen_getChildNodes(self, buf):        print >> buf, "    def getChildNodes(self):"        if len(self.argnames) == 0:            print >> buf, "        return ()"        else:            if self.hardest_arg < P_NESTED:                clist = ["self.%s" % c                         for c in self.argnames                         if self.argprops[c] == P_NODE]                if len(clist) == 0:                    print >> buf, "        return ()"                elif len(clist) == 1:                    print >> buf, "        return %s," % clist[0]                else:                    print >> buf, "        return %s" % COMMA.join(clist)            else:                print >> buf, "        nodelist = []"                template = "        nodelist.%s(%sself.%s%s)"                for name in self.argnames:                    if self.argprops[name] == P_NONE:                        tmp = ("        if self.%s is not None:\n"                               "            nodelist.append(self.%s)")                        print >> buf, tmp % (name, name)                    elif self.argprops[name] == P_NESTED:                        print >> buf, template % ("extend", "flatten_nodes(",                                                  name, ")")                    elif self.argprops[name] == P_NODE:                        print >> buf, template % ("append", "", name, "")                print >> buf, "        return tuple(nodelist)"     def _gen_repr(self, buf):        print >> buf, "    def __repr__(self):"        if self.argnames:            fmt = COMMA.join(["%s"] * self.nargs)            if '(' in self.args:                fmt = '(%s)' % fmt            vals = ["repr(self.%s)" % name for name in self.argnames]            vals = COMMA.join(vals)            if self.nargs == 1:                vals = vals + ","            print >> buf, '        return "%s(%s)" %% (%s)' % \                  (self.name, fmt, vals)        else:            print >> buf, '        return "%s()"' % self.name rx_init = re.compile('init\((.*)\):') def parse_spec(file):    classes = {}    cur = None    for line in fileinput.input(file):        if line.strip().startswith('#'):            continue        mo = rx_init.search(line)        if mo is None:            if cur is None:                # a normal entry                try:                    name, args = line.split(':')                except ValueError:                    continue                classes[name] = NodeInfo(name, args)                cur = None            else:                # some code for the __init__ method                cur.init.append(line)        else:            # some extra code for a Node's __init__ method            name = mo.group(1)            cur = classes[name]    return sorted(classes.values(), key=lambda n: n.name) def main():    prologue, epilogue = load_boilerplate(sys.argv[-1])    print prologue    print    classes = parse_spec(SPEC)    for info in classes:        print info.gen_source()    print epilogue if __name__ == "__main__":    main()    sys.exit(0) ### PROLOGUE"""Python abstract syntax node definitions This file is automatically generated by Tools/compiler/astgen.py"""from consts import CO_VARARGS, CO_VARKEYWORDS def flatten(seq):    l = []    for elt in seq:        t = type(elt)        if t is tuple or t is list:            for elt2 in flatten(elt):                l.append(elt2)        else:            l.append(elt)    return l def flatten_nodes(seq):    return [n for n in flatten(seq) if isinstance(n, Node)] nodes = {} class Node:    """Abstract base class for ast nodes."""    def getChildren(self):        pass # implemented by subclasses    def __iter__(self):        for n in self.getChildren():            yield n    def asList(self): # for backwards compatibility        return self.getChildren()    def getChildNodes(self):        pass # implemented by subclasses class EmptyNode(Node):    pass class Expression(Node):    # Expression is an artificial node class to support "eval"    nodes["expression"] = "Expression"    def __init__(self, node):        self.node = node     def getChildren(self):        return self.node,     def getChildNodes(self):        return self.node,     def __repr__(self):        return "Expression(%s)" % (repr(self.node)) ### EPILOGUEfor name, obj in globals().items():    if isinstance(obj, type) and issubclass(obj, Node):        nodes[name.lower()] = obj