How to write a csv file in binary mode?

Question

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

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

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Answer 1

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

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.

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

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)