[Python-3000] TextIOWrapper.write(s:str) and bytes in py3k-struni (original) (raw)

Christian Heimes lists at cheimes.de
Tue Jul 17 03:22:13 CEST 2007

Guido van Rossum wrote:

I came across this in your SF patch. I disagree with your desire to let TextIOWrapper.write() handle bytes: it should only be passed str objects. The uu test was failing because it was writing bytes to a text stream.

Perhaps the error should be better; though I'm not sure I want to add explicit type checks (as it would defeat duck typing).

Yes, duck typing is very useful but this duck doesn't quack me why it hurts. ;) It's rather confusing at first.

What do you think about

def write(self, s: str):
    if self.closed:
        raise ValueError("write to closed file")
    try:
        b = s.encode(self._encoding)
    except AttributeError:
        raise TypeError("str expected, got %r" % s)
    ...

def write(self, s: str):
    if self.closed:
        raise ValueError("write to closed file")
    if not hasattr(s, 'encode')
        raise TypeError("str expected, got %r" % s)
    ...

? It explains what is going wrong.

Christian

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