from ast import *

def makefunc(name):
    return FunctionDef(name=name,
        args=arguments(
            args=[],
            vararg=None,
            kwarg=None,
            defaults=[],
            kwonlyargs=[],
            kw_defaults=[]
        ),
        body=[ Pass() ],
        decorator_list=[]
    )

m = parse("""
def foo():
    pass
""")

m.body.append(makefunc('bar'))
fix_missing_locations(m)

compile(m, 'string', 'exec')