Xuanji Li <[email protected]> added the comment:
I don't fully understand Lib/urllib/request.py either, I just ported it and ran
the unittests... it seems like what it does is that if you send an iterator
through as 'data' you can't know the length in advance, and rather than let the
len(data) raise an exception catlee thought it's better to raise an exception
to tell the user exactly why the code failed (ie, because the user sent an
iterator and there's no way to meaningfully find the Content-Length of that).
As for the catching exceptions vs using isinstance: I thought about it for a
while, I think something like this feels right to me:
try:
self.sock.sendall(data)
except TypeError:
if isinstance(data, collections.Iterable):
for d in t:
self.sock.sendall(d)
else:
raise TypeError("data should be a bytes-like object or an iterable,
got %r" % type(it))
anyway, calling iter(data) is equivalent to calling data.__iter__(), so
catching the exception is equivalent to hasattr(data, '__iter__'), which is
roughly the same as isinstance(data, collections.Iterable). so we try the most
straightforward method (sending everything) then if that fails, data is either
an iterator or a wrong type.
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<http://bugs.python.org/issue3243>
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