問題描述

python 的 csv writer 不再支持二進制模式了嗎?

Does python's csv writer not support binary mode anymore?

直到現在我才不得不在 'b' 模式下寫入，但我遇到了非常煩人的錯誤，如下所示:

I haven't had to write in 'b' mode until now and i'm getting very annoying errors like so:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-2-030fb0c9dc9a> in <module>()
  4 with open('test.csv', 'wb') as f:
  5     w = csv.writer(f)
----> 6     w.writerows(rows)

TypeError: a bytes-like object is required, not 'str'

代碼:

import csv

rows = [b'1,2,3', b'4,5,6', b'7,8,9']
with open('test.csv', 'wb') as f:
    w = csv.writer(f)
    w.writerows(rows)

如果有人能解釋錯誤，那就太好了.我傳入了一個迭代，其中每個元素都是一個字節序列，但我仍然收到一個錯誤，即輸入不是字節"而是str".這種行為似乎出乎意料.

If anyone could explain the error that would be great. I'm passing in an iterable where every element is a byte sequence but I still get an error about the input not being 'bytes' but instead being 'str.' This behavior seems unexpected.

我知道如果我關閉二進制模式，上面的代碼片段可以寫入普通文件.如果有人有建設性的解決方案或建議，我將非常感激.

I know the above code snippet can write to a normal file if I turn off the binary mode. If anyone has a solution or suggestion that is constructive I would very much appreciate it.

推薦答案

Python 3 中的 csv 模塊總是嘗試寫入字符串，而不是字節:

The csv module in Python 3 always attempts to write strings, not bytes:

為了盡可能輕松地與實現 DB API 的模塊進行交互，值 None 被寫為空字符串.[...] 所有其他非字符串數據在寫入之前都使用 str() 進行字符串化.

To make it as easy as possible to interface with modules which implement the DB API, the value None is written as the empty string. [...] All other non-string data are stringified with str() before being written.

這意味著你必須向它傳遞一個接受字符串的文件對象，這通常意味著以文本模式打開它.

That means you have to pass it a file object that accepts strings, which usually means opening it in text mode.

如果您遇到需要字節的文件對象，請將其包裝在 io.TextIOWrapper 處理 str->bytes 編碼:

If you are stuck with a file object that wants bytes, wrap it in an io.TextIOWrapper to handle str->bytes encoding:

# assuming you want utf-8
with io.TextIOWrapper(binary_file, encoding='utf-8', newline='') as text_file:
    w = csv.writer(text_file)

這篇關于如何以二進制模式編寫csv文件?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！