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gh-100226: Clarify StreamReader.read behavior #101807

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Merged
merged 5 commits into from
Feb 17, 2023
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gh-100226: Clarify StreamReader.read behavior #101807

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cce42af
Clarify StreamReader.read behavior
jgosmann Feb 10, 2023
970b725
Apply suggestions from code review
jgosmann Feb 16, 2023
d5f28eb
Improve clarity of StreamReader.read docs
jgosmann Feb 16, 2023
976c25e
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jgosmann Feb 17, 2023
a920fbe
Copy StreamReader.read documentation to docstring
jgosmann Feb 17, 2023
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12 changes: 10 additions & 2 deletions Doc/library/asyncio-stream.rst
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Expand Up @@ -206,12 +206,20 @@ StreamReader

.. coroutinemethod:: read(n=-1)

Read up to *n* bytes. If *n* is not provided, or set to ``-1``,
read until EOF and return all read bytes.
Read up to *n* bytes from the stream.

If *n* is not provided or set to ``-1``,
read until EOF, then return all read :class:`bytes`.
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As a beginning reader, before having read @jgosmann 's detailed explaination and @gvanrossum 's summary, I was evidently confused here about what "until EOF" specifically meant in this context. It therefore might warrant some more clarity here, but maybe its just my lack of subject matter expertise compared with the target audience.

If EOF was received and the internal buffer is empty,
return an empty ``bytes`` object.

If *n* is ``0``, return an empty ``bytes`` object immediately.

If *n* is positive, return at most *n* available ``bytes``
as soon as at least 1 byte is available in the internal buffer.
If EOF is received before any byte is read, return an empty
``bytes`` object.

.. coroutinemethod:: readline()

Read one line, where "line" is a sequence of bytes
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17 changes: 9 additions & 8 deletions Lib/asyncio/streams.py
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Expand Up @@ -649,16 +649,17 @@ async def readuntil(self, separator=b'\n'):
async def read(self, n=-1):
"""Read up to `n` bytes from the stream.

If n is not provided, or set to -1, read until EOF and return all read
bytes. If the EOF was received and the internal buffer is empty, return
an empty bytes object.
If `n` is not provided or set to -1,
read until EOF, then return all read bytes.
If EOF was received and the internal buffer is empty,
return an empty bytes object.

If n is zero, return empty bytes object immediately.
If `n` is 0, return an empty bytes object immediately.

If n is positive, this function try to read `n` bytes, and may return
less or equal bytes than requested, but at least one byte. If EOF was
received before any byte is read, this function returns empty byte
object.
If `n` is positive, return at most `n` available bytes
as soon as at least 1 byte is available in the internal buffer.
If EOF is received before any byte is read, return an empty
bytes object.

Returned value is not limited with limit, configured at stream
creation.
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