12.6.3.1 use commands of the Wave library to process sound files. 

Wave library. Sound processing.

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

To open a *.wav file, use the function open()

wave.open(filename, mode=None)

filename - *.wav file which is in the *.py file directory.

mode = 'rb' - read-only mode.
mode = 'wb' - record-only mode.

import wave
 
source = wave.open("in.wav", mode="rb")  # open file for reading
dest = wave.open("out.wav", mode="wb")   # open file for writingDownload in.wav

wave.close() - close *.wav file.

source.close()
dest.close()

to pass parameters from read file to write file use...

dest.setparams(source.getparams())

Frames of *.wav file

To get all the frames from an audio file, use the getnframes() function

frames_count = source.getnframes()Read frames in *.wav file

wave.readframes(wave.getnframes()) # read all frames from *.wav file. 

Get information about wav-file

You can use:
(nchannels, sampwidth, framerate, nframes, comptype, compname) = source.getparams()
# getnchannels()  - returns number of audio channels (1 for mono, 2 for stereo)
# getsampwidth()  - returns sample width in bytes
# getframerate()  - returns sampling frequency
# getnframes()    - returns number of audio frames

Struct library

struct library — Interpret bytes as packed binary data

The pack() and unpack() methods. Packing and unpacking data.

struct.pack(format, v1, v2, ...)
Return a bytes object containing the values v1, v2, … packed according to the format string format. Allows you to pack audio fragment frames into a file.

struct.unpack(format, buffer)
Unpack from the buffer according to string format. Allows you to extract audio fragment frames to a file. The result is a tuple even if it contains exactly one item.import wave
import struct

source = wave.open("in.wav", mode="rb")
dest = wave.open("out.wav", mode="wb")
# copy parameters from source to dest
dest.setparams(source.getparams())
# find the number of frames
frames_count = source.getnframes() 
# unpack all frames of in.wav to the list data 
data = struct.unpack("<" + str(frames_count) + "h",                            source.readframes(frames_count))
# the main line of the program - reverse the list
newdata = data[::-1] 
# pack all frames of data to the list newframes
newframes = struct.pack("<" + str(len(newdata)) + "h", *newdata) 
# write content to the converted file out.wav
dest.writeframes(newframes) 
source.close()
dest.close()Attention!!! In this tutorial, we will be working with *.wav audio files that are encoded unsigned 8-bit PCM in Audacity.

Questions:

Exercises:

Tasks:

Tasks on Stepik.org course "Python Programming for NIS"

1. Task  "Copy *.wav file" Download in.wav.

   Open in program file in.wav and create copy to out.wav.

2. Task "Count frames"

   Output count frames of file in.wav.

3. Task "Half sound"

   Output the first half part of file in.wav.

4. Task "Reverse sound"

   Output to the out.wav reverse of file in.wav.

5. Task "Speed up twice"

   Write a program to speed up a file in.wav twice.

6. Task "Slow down twice"

   Write a program to slow down the sound twice of file  in.wav.