22.4. "wave" --- Read and write WAV files
*****************************************

**Source code:** Lib/wave.py

======================================================================

The "wave" module provides a convenient interface to the WAV sound
format. It does not support compression/decompression, but it does
support mono/stereo.

The "wave" module defines the following function and exception:

wave.open(file, mode=None)

   If *file* is a string, open the file by that name, otherwise treat
   it as a file-like object.  *mode* can be:

   "'rb'"
      Read only mode.

   "'wb'"
      Write only mode.

   Note that it does not allow read/write WAV files.

   A *mode* of "'rb'" returns a "Wave_read" object, while a *mode* of
   "'wb'" returns a "Wave_write" object.  If *mode* is omitted and a
   file-like object is passed as *file*, "file.mode" is used as the
   default value for *mode*.

   If you pass in a file-like object, the wave object will not close
   it when its "close()" method is called; it is the caller's
   responsibility to close the file object.

   The "open()" function may be used in a "with" statement.  When the
   "with" block completes, the "Wave_read.close()" or
   "Wave_write.close()" method is called.

   3.4 版更變: Added support for unseekable files.

wave.openfp(file, mode)

   A synonym for "open()", maintained for backwards compatibility.

exception wave.Error

   An error raised when something is impossible because it violates
   the WAV specification or hits an implementation deficiency.


22.4.1. Wave_read Objects
=========================

Wave_read objects, as returned by "open()", have the following
methods:

Wave_read.close()

   Close the stream if it was opened by "wave", and make the instance
   unusable.  This is called automatically on object collection.

Wave_read.getnchannels()

   Returns number of audio channels ("1" for mono, "2" for stereo).

Wave_read.getsampwidth()

   Returns sample width in bytes.

Wave_read.getframerate()

   Returns sampling frequency.

Wave_read.getnframes()

   Returns number of audio frames.

Wave_read.getcomptype()

   Returns compression type ("'NONE'" is the only supported type).

Wave_read.getcompname()

   Human-readable version of "getcomptype()". Usually "'not
   compressed'" parallels "'NONE'".

Wave_read.getparams()

   Returns a "namedtuple()" "(nchannels, sampwidth, framerate,
   nframes, comptype, compname)", equivalent to output of the "get*()"
   methods.

Wave_read.readframes(n)

   Reads and returns at most *n* frames of audio, as a "bytes" object.

Wave_read.rewind()

   Rewind the file pointer to the beginning of the audio stream.

The following two methods are defined for compatibility with the
"aifc" module, and don't do anything interesting.

Wave_read.getmarkers()

   Returns "None".

Wave_read.getmark(id)

   Raise an error.

The following two methods define a term "position" which is compatible
between them, and is otherwise implementation dependent.

Wave_read.setpos(pos)

   Set the file pointer to the specified position.

Wave_read.tell()

   Return current file pointer position.


22.4.2. Wave_write Objects
==========================

For seekable output streams, the "wave" header will automatically be
updated to reflect the number of frames actually written.  For
unseekable streams, the *nframes* value must be accurate when the
first frame data is written.  An accurate *nframes* value can be
achieved either by calling "setnframes()" or "setparams()" with the
number of frames that will be written before "close()" is called and
then using "writeframesraw()" to write the frame data, or by calling
"writeframes()" with all of the frame data to be written.  In the
latter case "writeframes()" will calculate the number of frames in the
data and set *nframes* accordingly before writing the frame data.

Wave_write objects, as returned by "open()", have the following
methods:

3.4 版更變: Added support for unseekable files.

Wave_write.close()

   Make sure *nframes* is correct, and close the file if it was opened
   by "wave".  This method is called upon object collection.  It will
   raise an exception if the output stream is not seekable and
   *nframes* does not match the number of frames actually written.

Wave_write.setnchannels(n)

   Set the number of channels.

Wave_write.setsampwidth(n)

   Set the sample width to *n* bytes.

Wave_write.setframerate(n)

   Set the frame rate to *n*.

   3.2 版更變: A non-integral input to this method is rounded to the
   nearest integer.

Wave_write.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).

Wave_write.setcomptype(type, name)

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

Wave_write.setparams(tuple)

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

Wave_write.tell()

   Return current position in the file, with the same disclaimer for
   the "Wave_read.tell()" and "Wave_read.setpos()" methods.

Wave_write.writeframesraw(data)

   Write audio frames, without correcting *nframes*.

   3.4 版更變: Any *bytes-like object* is now accepted.

Wave_write.writeframes(data)

   Write audio frames and make sure *nframes* is correct.  It will
   raise an error if the output stream is not seekable and the total
   number of frames that have been written after *data* has been
   written does not match the previously set value for *nframes*.

   3.4 版更變: Any *bytes-like object* is now accepted.

Note that it is invalid to set any parameters after calling
"writeframes()" or "writeframesraw()", and any attempt to do so will
raise "wave.Error".
