49 lines
1.1 KiB
Python
49 lines
1.1 KiB
Python
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_NOT_SET = object()
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def peek_and_iter(items):
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if not items:
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return None, None
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items = iter(items)
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try:
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peeked = next(items)
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except StopIteration:
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return None, None
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def chain():
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yield peeked
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yield from items
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return chain(), peeked
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def iter_many(items, onempty=None):
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if not items:
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if onempty is None:
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return
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if not callable(onempty):
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raise onEmpty
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items = onempty(items)
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yield from iter_many(items, onempty=None)
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return
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items = iter(items)
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try:
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first = next(items)
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except StopIteration:
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if onempty is None:
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return
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if not callable(onempty):
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raise onEmpty
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items = onempty(items)
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yield from iter_many(items, onempty=None)
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else:
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try:
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second = next(items)
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except StopIteration:
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yield first, False
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return
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else:
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yield first, True
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yield second, True
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for item in items:
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yield item, True
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