写入 CSV 文件。 TypeError：writerows() 参数必须是可迭代的

Question

我正在尝试编写一个货币转换器，其中包含代码和一个 csv 文件，可以在其中编辑 csv 文件以保存使用之间的新汇率。但我在写入文件和更改速率时遇到问题：

 def change():
    print()
    print()
    print()
    print("1) Change existing exchange rate.")
    print("2) Add new exchange rates.")
    print("3) Quit.")
    exRtFile = open ('exchangeRate.csv')
    exchReader = csv.reader(exRtFile)
    exchWriter = csv.writer(exRtFile)
    loop2=0
    while loop2==0:
        selected=int(input("Please select an option: "))
        if selected == 1:
            change = input("What rate would you like to change: ")
            changeRt = float(input("What would you like to change the rate to: "))
            for row in exchReader:
                currency = row[0]
                if currency == change:
                    crntRt = row[1]
                    crntRt = changeRt
                    exchWriter.writerows(crntRt)

输入/输出示例：

1) Change existing exchange rate.
2) Add new exchange rates.
3) Quit.
Please select an option: 1
What rate would you like to change: Euro
What would you like to change the rate to: 1.23
Traceback (most recent call last):
  File "<pyshell#7>", line 1, in <module>
    converter()
  File "py", line 21, in converter
    change()
  File "py", line 91, in change
    exchWriter.writerows(crntRt)
TypeError: writerows() argument must be iterable

Answer 1

writeRows() 就其本质而言，期望一个变量保存一堆值，每个值都包含要写入输出文件中一行的数据。

因为你给 writerows() 一个单一的 float 值，它的响应是告诉你它不知道如何把它变成多行——在“Python speak”中，must be iterable 的意思是“我不能弄清楚如何从你给我的项目中获取多个值”。

您的代码中可能还有许多其他问题。特别是：

 crntRt = row[1]
 crntRt = changeRt
 exchWriter.writerows(crntRt)

让我觉得您希望在输出中看到 row[1] 的值，但您不会，因为下一行用新汇率覆盖了该值。