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bpo-34764: improve docs example of iter() with sentinel value (GH-11222)

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Chris Rands 2018-12-24 06:07:17 +01:00 • committed by Raymond Hettinger
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commit d378b1f8ed
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13
Doc/library/functions.rst
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@ -810,13 +810,14 @@ are always available. They are listed here in alphabetical order.
See also :ref:`typeiter`.
One useful application of the second form of :func:`iter` is to read lines of
a file until a certain line is reached. The following example reads a file
until the :meth:`~io.TextIOBase.readline` method returns an empty string::
One useful application of the second form of :func:`iter` is to build a
block-reader. For example, reading fixed-width blocks from a binary
database file until the end of file is reached::
with open('mydata.txt') as fp:
for line in iter(fp.readline, ''):
process_line(line)
from functools import partial
with open('mydata.db', 'rb') as f:
for block in iter(partial(f.read, 64), ''):
process_block(block)
.. function:: len(s)