[issue27613] Empty iterator with fake __len__ is rendered as a single bracket ] when using json's iterencode

[Raymond Hettinger]

Raymond Hettinger added the comment:

Per PEP-8, the Python preferred-style is, "For sequences, (strings, lists, tuples), use the fact that empty sequences are false."

    Yes: if not seq:
        if seq:

    No: if len(seq):
        if not len(seq):

The Python libraries are not obliged to defend themselves against non-sensical types (i.e. defining an empty iterator as a subclass of list and returning a non-zero len).

I recommend leaving the code as-is and closing a "not a bug".  In a way, this report is no more interesting than observing that a __hash__ that returns a random value on each call doesn't work well in a dictionary.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue27613>
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