Python 向csv文件添加更多新数据时出现问题

我写了这个程序，但显然不起作用。我是说代码的最后一部分。程序正在创建文件并向csv文件添加一些内容。代码的最后一部分应该向已经存在的文件中添加更多的数据，但是每次我想运行这个程序时，我都会遇到这样的错误：

Traceback (most recent call last):
  File "/Users/grzegorzspytek/Desktop/Sending_automated_mails/nw_csv.py", line 121, in <module>
    for row in reader:
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/csv.py", line 111, in __next__
    self.fieldnames
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/csv.py", line 98, in fieldnames
    self._fieldnames = next(self.reader)
_csv.Error: iterator should return strings, not bytes (did you open the file in text mode?)

---

您应该改为以文本模式打开临时文件：

temp_file = NamedTemporaryFile(mode='w+', delete=False)

---

否则，默认情况下，临时文件以二进制模式打开。

不幸的是，它仍然没有像以前一样工作：回溯（最近一次调用）文件“/Users/grzegorzspytek/Desktop/python/Sending_automated_mails/nw_csv.py”，第125行，在“Email”：行[“Email”]文件中“/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/csv.py”，第155行，在writerow中返回self.writer.writerow（self.\u dict\u to_list（rowdict））文件“/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/tempfile.py”，第481行，在func\u包装器返回func（*args，**kwargs）TypeError:abytes-like对象是必需的，我知道不是'str'。我已经用一个更合适的解决方案更新了我的答案。你试过了吗？我把它放到编译器中，得到了一个要求字符串而不是字节的错误。是的，我试过了。在将模式指定为

w+

后，它工作了。对于二进制模式，默认模式是

w+b

，这就是why

csv.writer

在您的代码中引发异常。我添加了您在上面放弃的行，并将open（“rb”）更改为open（“r+”）。它现在可以工作了。谢谢。

import csv
import shutil
import os
from tempfile import NamedTemporaryFile


def get_len(path):
    with open(path, "r") as csvfile:
        reader = csv.reader(csvfile)
        read_list = list(reader)
    return len(read_list)

#check if this is the file,
def append_data(path, name, email):
    if not os.path.isfile(path):
        with open(path, "w") as csvfile:
            fieldnames = ["ID", "Name", "Email"]
            writer = csv.DictWriter(csvfile, fieldnames = fieldnames)
            writer.writeheader()
            print("Creating file...")

    with open(path, "a") as csvfile:
        fieldnames = ["ID", "Name", "Email"]
        writer = csv.DictWriter(csvfile, fieldnames = fieldnames)
        writer.writerow({
            "ID": get_len(path),
            "Name": name,
            "Email": email
        })
        print("Adding data for " + name)



path = "/Users/grzegorzspytek/Desktop/Sending_automated_mails/data.csv"
append_data(path, "grzesiek", "grz.spy")

filename = "data.csv"
temp_file = NamedTemporaryFile(delete=False)





with open("data.csv", "rb") as csvfile, temp_file:
    reader = csv.DictReader(csvfile)
    fieldnames = ["ID", "Name", "Email"]
    writer = csv.DictWriter(temp_file, fieldnames = fieldnames)
    for row in reader:
        writer.writerow({
            "ID": row["ID"],
            "Name": row["Name"],
            "Email": row["Email"]
        })

temp_file = NamedTemporaryFile(mode='w+', delete=False)