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# 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.

  Changed in version 3.4: 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 string of bytes.

`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:

Changed in version 3.4: 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.

  Changed in version 3.2: 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.

  Changed in version 3.4: 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.

  Changed in version 3.4: 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`.

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