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GH-132445: Allowing to reset parameters of Wave_write #132448

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GH-132445: Allowing to reset parameters of Wave_write #132448

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30 changes: 28 additions & 2 deletions Doc/library/wave.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -198,11 +198,20 @@ Wave_write Objects

Set the number of channels.

Raises an :exc:`wave.Error`, if the value is set after data was written.
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Suggested change
Raises an :exc:`wave.Error`, if the value is set after data was written.
Raise :exc:`wave.Error` if a different value is set after data was written.


.. versionchanged:: 3.14
:exc:`wave.Error` is not raised, if the value is the same.
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Suggested change
.. versionchanged:: 3.14
:exc:`wave.Error` is not raised, if the value is the same.
.. versionchanged:: next
No :exc:`wave.Error` is raised if the value does not change.

Same for the rest of the docs.


.. method:: setsampwidth(n)

Set the sample width to *n* bytes.

Raises an :exc:`wave.Error`, if the value is set after data was written.

.. versionchanged:: 3.14
:exc:`wave.Error` is not raised, if the value is the same.


.. method:: setframerate(n)

Expand All @@ -212,26 +221,43 @@ Wave_write Objects
A non-integral input to this method is rounded to the nearest
integer.

Raises an :exc:`wave.Error`, if the value is set after data was written.

.. versionchanged:: 3.14
:exc:`wave.Error` is not raised, if the value is the same.


.. method:: setnframes(n)

Set the number of frames to *n*. This will be changed later if the number
of frames actually written is different (this update attempt will
raise an error if the output stream is not seekable).

Raises an :exc:`wave.Error`, if the value is set after data was written.

.. versionchanged:: 3.14
:exc:`wave.Error` is not raised, if the value is the same.

.. method:: setcomptype(type, name)

Set the compression type and description. At the moment, only compression type
``NONE`` is supported, meaning no compression.

Raises an Error, if the value is set after data was written.

.. versionchanged:: 3.14
:exc:`wave.Error` is not raised, if the value is the same.

.. method:: setparams(tuple)

The *tuple* should be ``(nchannels, sampwidth, framerate, nframes, comptype,
compname)``, with values valid for the ``set*()`` methods. Sets all
parameters.

Raises an :exc:`wave.Error`, if the value is set after data was written.

.. versionchanged:: 3.14
:exc:`wave.Error` is not raised, if the value is the same.

.. method:: tell()

Expand All @@ -257,6 +283,6 @@ Wave_write Objects
.. versionchanged:: 3.4
Any :term:`bytes-like object` is now accepted.

Note that it is invalid to set any parameters after calling :meth:`writeframes`
Note that it is invalid to change any parameters after calling :meth:`writeframes`
or :meth:`writeframesraw`, and any attempt to do so will raise
:exc:`wave.Error`.
:exc:`wave.Error`, if the value is different from the current value.
33 changes: 33 additions & 0 deletions Lib/test/test_wave.py
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Expand Up @@ -162,6 +162,39 @@ def test_write_deprecations(self):
with self.assertWarns(DeprecationWarning):
self.assertIsNone(writer.getmarkers())

def test_setters(self):
with io.BytesIO(b'') as tmpfile:
with wave.open(tmpfile, 'wb') as writer:
writer.setnchannels(1)
writer.setsampwidth(1)
writer.setframerate(1)
writer.setcomptype('NONE', 'not compressed')

# no errors, when chaning and nothing was written
writer.setnchannels(2)
writer.setsampwidth(2)
writer.setframerate(2)
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We also need to test rounded values.

writer.setcomptype('NONE', 'uncompressed')

# write some frames
writer.writeframes(b'\0' * 16)

# changeing now should result in an error
with self.assertRaises(wave.Error):
writer.setnchannels(1)
with self.assertRaises(wave.Error):
writer.setsampwidth(1)
with self.assertRaises(wave.Error):
writer.setframerate(1)
with self.assertRaises(wave.Error):
writer.setcomptype('NONE', 'other')

# same value, so it should not raise Error
writer.setnchannels(2)
writer.setsampwidth(2)
writer.setframerate(2)
writer.setcomptype('NONE', 'uncompressed')


class WaveLowLevelTest(unittest.TestCase):

Expand Down
19 changes: 10 additions & 9 deletions Lib/wave.py
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Expand Up @@ -478,7 +478,7 @@ def __exit__(self, *args):
# User visible methods.
#
def setnchannels(self, nchannels):
if self._datawritten:
if self._datawritten and self._nchannels != nchannels:
raise Error('cannot change parameters after starting to write')
if nchannels < 1:
raise Error('bad # of channels')
Expand All @@ -490,7 +490,7 @@ def getnchannels(self):
return self._nchannels

def setsampwidth(self, sampwidth):
if self._datawritten:
if self._datawritten and self._sampwidth != sampwidth:
raise Error('cannot change parameters after starting to write')
if sampwidth < 1 or sampwidth > 4:
raise Error('bad sample width')
Expand All @@ -502,27 +502,28 @@ def getsampwidth(self):
return self._sampwidth

def setframerate(self, framerate):
if self._datawritten:
rounded_framerate = int(round(framerate))
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The int(round(framerate)) should be tested when two distinct input framerates give the same rounded framerate.

if self._datawritten and self._framerate != rounded_framerate:
raise Error('cannot change parameters after starting to write')
if framerate <= 0:
if rounded_framerate <= 0:
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I noticed that before this change we could write self.setframerate(0.5) and the framerate would be set to 0. With this change, we prevent a bad framerate.

So also test that self.setframerate(0.5) raises an exception, but not self.setframerate(0.51).

raise Error('bad frame rate')
self._framerate = int(round(framerate))
self._framerate = rounded_framerate

def getframerate(self):
if not self._framerate:
raise Error('frame rate not set')
return self._framerate

def setnframes(self, nframes):
if self._datawritten:
if self._datawritten and self._nframes != nframes:
raise Error('cannot change parameters after starting to write')
self._nframes = nframes

def getnframes(self):
return self._nframeswritten

def setcomptype(self, comptype, compname):
if self._datawritten:
if self._datawritten and (self._comptype != comptype or self._compname != compname):
raise Error('cannot change parameters after starting to write')
if comptype not in ('NONE',):
raise Error('unsupported compression type')
Expand All @@ -537,8 +538,8 @@ def getcompname(self):

def setparams(self, params):
nchannels, sampwidth, framerate, nframes, comptype, compname = params
if self._datawritten:
raise Error('cannot change parameters after starting to write')
# no check for value change required: either the properties have the same
# value or they throw the exception them selfs
self.setnchannels(nchannels)
self.setsampwidth(sampwidth)
self.setframerate(framerate)
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2025-04-30-18-12-53.gh-issue-132445.zPEifv.rst
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@@ -0,0 +1 @@
:class:`Wave_write` setters don't raise an error anymore, if the value did not change after frames were written.
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