def run(input=sys.stdin, output=sys.stdout):
    r"""CouchDB view function handler implementation for Python.

    :param input: the readable file-like object to read input from
    :param output: the writable file-like object to write output to
    """
    functions = []

    def _writejson(obj):
        obj = json.encode(obj)
        if isinstance(obj, util.utype):
            obj = obj.encode('utf-8')
        output.write(obj)
        output.write(b'\n')
        output.flush()

    def _log(message):
        if not isinstance(message, util.strbase):
            message = json.encode(message)
        _writejson({'log': message})

    def reset(config=None):
        del functions[:]
        return True

    def add_fun(string):
        string = BOM_UTF8 + string.encode('utf-8')
        globals_ = {}
        try:
            util.pyexec(string, {'log': _log}, globals_)
        except Exception as e:
            return {'error': {
                'id': 'map_compilation_error',
                'reason': e.args[0]
            }}
        err = {'error': {
            'id': 'map_compilation_error',
            'reason': 'string must eval to a function '
                      '(ex: "def(doc): return 1")'
        }}
        if len(globals_) != 1:
            return err
        function = list(globals_.values())[0]
        if type(function) is not FunctionType:
            return err
        functions.append(function)
        return True

    def map_doc(doc):
        results = []
        for function in functions:
            try:
                results.append([[key, value] for key, value in function(doc)])
            except Exception as e:
                log.error('runtime error in map function: %s', e,
                          exc_info=True)
                results.append([])
                _log(traceback.format_exc())
        return results

    def reduce(*cmd, **kwargs):
        code = BOM_UTF8 + cmd[0][0].encode('utf-8')
        args = cmd[1]
        globals_ = {}
        try:
            util.pyexec(code, {'log': _log}, globals_)
        except Exception as e:
            log.error('runtime error in reduce function: %s', e,
                      exc_info=True)
            return {'error': {
                'id': 'reduce_compilation_error',
                'reason': e.args[0]
            }}
        err = {'error': {
            'id': 'reduce_compilation_error',
            'reason': 'string must eval to a function '
                      '(ex: "def(keys, values): return 1")'
        }}
        if len(globals_) != 1:
            return err
        function = list(globals_.values())[0]
        if type(function) is not FunctionType:
            return err

        rereduce = kwargs.get('rereduce', False)
        results = []
        if rereduce:
            keys = None
            vals = args
        else:
            if args:
                keys, vals = zip(*args)
            else:
                keys, vals = [], []
        if util.funcode(function).co_argcount == 3:
            results = function(keys, vals, rereduce)
        else:
            results = function(keys, vals)
        return [True, [results]]

    def rereduce(*cmd):
        # Note: weird kwargs is for Python 2.5 compat
        return reduce(*cmd, **{'rereduce': True})

    handlers = {'reset': reset, 'add_fun': add_fun, 'map_doc': map_doc,
                'reduce': reduce, 'rereduce': rereduce}

    try:
        while True:
            line = input.readline()
            if not line:
                break
            try:
                cmd = json.decode(line)
                log.debug('Processing %r', cmd)
            except ValueError as e:
                log.error('Error: %s', e, exc_info=True)
                return 1
            else:
                retval = handlers[cmd[0]](*cmd[1:])
                log.debug('Returning  %r', retval)
                _writejson(retval)
    except __HOLE__:
        return 0
    except Exception as e:
        log.error('Error: %s', e, exc_info=True)
        return 1
dataset/ETHPy150Open djc/couchdb-python/couchdb/view.py/run