PyAST is a library that allows for creating AST structures using declarative programming form.

example:

== jsast.py ==

import pyast as ast

class Node(ast.Node):
    pass

class Statement(Node):
    pass

class Expression(Pattern):
    pass

class Operator(Node):
    token = ast.field(("+","=","-","==","!=",">",">"))

class Identifier(Expression):
    name = ast.field((str, unicode))

class Literal(Expression):
    value = ast.field((str, bool, int, NoneType))

class Program(ast.Node):
    body = ast.seq(Statement, null=True)

class ExpressionStatement(Statement):
    expression = ast.field(Expression)

class AssignmentExpression(Expression):
    operator = ast.field(Operator)
    left = ast.field(Expression)
    right = ast.field(Expression)

== main.py ==

from jsast import *

prog = Program()
prog.body.append(
    ExpressionStatement(
        AssignmentExpression(
            Operator("="),
            Identifier("x"),
            Literal(2)
        )))

# result: x=2;
=========

pyast.DEBUG variable defines if pyast operates in DEBUG mode in which the 
strong typing is enforced at cost of performance, or optimized mode when all
the checks are inactive.