Why do I get ValueError: dict contains fields not in fieldnames when trying to write Python dict to csv?

Question

我遇到了这个错误

ValueError: dict contains fields not in fieldnames: 'bobama', 'mfisc', 'nhay', 'bgates', 'jdoe', 'sburry', 'mcuban'

使用以下代码：

class Authentication:
    def __init__(self):
        # instantiate an instance variable
        self.user_dict = {}

    def register_user(self, uname, passwd):
        if uname in self.user_dict:
            print("Username exists! Try a new one.")
            return False
        else:
            self.user_dict[uname] = passwd
            print("Registration successful" )
            return True    

def data_entry(auth):

    # registering 3 users
    auth.register_user('jdoe', '4^%$') # Jane Doe
    auth.register_user('sburry', '456@#&^') # Sam Burry
    auth.register_user('mfisc', '%6&#$@#') # Mike Fischer
    auth.register_user('nhay', 'ildfu45') # Nicky Hailey
    auth.register_user('bobama', 'klj43509jafd') # Barack Obama
    auth.register_user('bgates', '^&%kjsfd934@#$') # Bill Gates 
    auth.register_user('mcuban', '9&4rl#nsf') # Mark Cuban

# Main program
auth = Authentication()
data_entry(auth)

dictt = auth.user_dict

import csv

class AuthenticationIOcsv(Authentication):
    def write_info(self):
        fname='userinfo.csv'        
        with open(fname,'w') as op_file:

            field_names = ['Username', 'Password']

            op_writer = csv.DictWriter(op_file, fieldnames=field_names)

            op_writer.writeheader()

            op_writer.writerow(dictt)        

# Main Program
auth = AuthenticationIOcsv()
data_entry(auth)

# writing to file
auth.write_info()

该项目的目的是使用继承和 child class 创建一个包含 headers 'Username' 和 [=27 列的 csv 文件=] 然后分别是这些列中的字典键和值。我玩弄了一些其他解决方案来将字典写入 csv，我可以 post 但结果是只有 headers 的空白 csv 文件或其他类型的错误。例如：

            op_writer = csv.DictWriter(op_file, fieldnames=field_names)

            op_writer.writeheader()

            for key, value in dictt.items():
                op_writer.writerow([key,value])

我收到这个错误：

AttributeError: 'list' object has no attribute 'keys'

我是 Python 的新手，因此非常感谢任何指导！我显然很难理解如何以导出到 excel 的方式访问字典项目。先感谢您。

Answer 1

这是一个DictWriter，只收到dict data。可以使用这种方式写入数据：

op_writer = csv.DictWriter(op_file, fieldnames=field_names)
op_writer.writeheader()
for username, pwd in dictt.items():
    op_writer.writerow({"Username": username, "Password": pwd})

Why do I get ValueError: dict contains fields not in fieldnames when trying to write Python dict to csv?

Why do I get ValueError: dict contains fields not in fieldnames when trying to write Python dict to csv?

python

csv

dictionary

python-3.x

export-to-csv