def isdefined(obj, force_import=False, namespace=None):
    """Return True if object is defined in namespace
    If namespace is None --> namespace = locals()"""
    if namespace is None:
        namespace = locals()
    attr_list = obj.split('.')
    base = attr_list.pop(0)
    if len(base) == 0:
        return False
    if base not in builtins.__dict__ and base not in namespace:
        if force_import:
            try:
                module = __import__(base, globals(), namespace)
                if base not in globals():
                    globals()[base] = module
                namespace[base] = module
            except Exception:
                return False
        else:
            return False
    for attr in attr_list:
        try:
            attr_not_found = not hasattr(eval(base, namespace), attr)
        except (SyntaxError, AttributeError):
            return False
        if attr_not_found:
            if force_import:
                try:
                    __import__(base+'.'+attr, globals(), namespace)
                except (ImportError, SyntaxError):
                    return False
            else:
                return False
        base += '.'+attr
    return True