尝试将字典写入CSV文件时，Str属性没有键

我正在尝试使用以下代码将字典写入CSV文件：

def condense_data(in_file, out_file, city):
"""
This function takes full data from the specified input file
and writes the condensed data to a specified output file. The city
argument determines how the input file will be parsed.

HINT: See the cell below to see how the arguments are structured!
"""

with open(out_file, 'w') as f_out, open(in_file, 'r') as f_in:
    # set up csv DictWriter object - writer requires column names for the
    # first row as the "fieldnames" argument

    out_colnames = ['duration', 'month', 'hour', 'day_of_week', 'user_type']        
    trip_writer = csv.DictWriter(f_out, fieldnames = out_colnames)
    trip_writer.writeheader()

    ## TODO: set up csv DictReader object ##
    trip_reader = csv.DictReader(f_in)

    # collect data from and process each row
    for row in trip_reader:
        # set up a dictionary to hold the values for the cleaned and trimmed
        # data point
        new_point = {}

        ## TODO: use the helper functions to get the cleaned data from  ##
        ## the original data dictionaries.                              ##
        ## Note that the keys for the new_point dictionary should match ##
        ## the column names set in the DictWriter object above.         ##

        duration = duration_in_mins(row, city)
        month, hour, day_of_week = time_of_trip(row, city)
        user_type = type_of_user(row, city)
        new_point = {'duration': duration, 'month': month, 'hour': hour,
                     'day_of_week': day_of_week, 'user_type': user_type}



        print(new_point) # Works fine till here, I am able print the right output
        trip_writer.writerows(new_point) # throws an error

下面是抛出的错误：

AttributeError Traceback（最近一次调用last）in（）8 9 for city，filenames in city_info.items（）：---> 10 condense_data（filenames ['in_file']，filenames ['out_file']，city）11 print_first_point （文件名['out_file']）在condense_data（in_file，out_file，city）中38 ##请参阅https://docs.python.org/3/library/csv.html#writer-objects## 39 print（new_point） - - > 40 trip_writer.writerows（new_point）41 42 /opt/conda/lib/python3.6/csv.py in writerows（self，rowdicts）156 157 def writer（（self，rowdicts）： - > 158返回self . writer.writerows（map（self._dict_to_list，rowdicts））159 160 #Wore Sniffer的类型检查反对在_dict_to_list（self，rowdict）中排除complex（）/opt/conda/lib/python3.6/csv.py的构建版本146 def _dict_to_list（self，rowdict）：147如果self.extrasaction ==“raise”： - > 148 wrong_fields = rowdict.keys（） - self.fieldnames 149 if wrong_fields：150引发ValueError（“dict包含不在fieldnames中的字段：” AttributeError：'str'对象没有属性'keys'

我确实在Stack Overflow上看到了这类问题，但没有一个有用 .