C4.py

import numpy as np
import wave

NOTE_FREQUENCY = 261.63 # C4
NOTE_LENGTH = 1.0 / NOTE_FREQUENCY
SAMPLE_LENGTH = 1000.0 * NOTE_LENGTH
SAMPLE_RATE = 44100.0

t = np.linspace(0, SAMPLE_LENGTH, int(SAMPLE_LENGTH * SAMPLE_RATE))
s = np.sin(2 * np.pi * NOTE_FREQUENCY * t)

# 16-bit little-endian
s = (s * (2 ** 15 - 1)).astype("<h")

with wave.open("C4.wav", "w") as f:
    f.setnchannels(2)
    f.setsampwidth(2)
    f.setframerate(SAMPLE_RATE)
    f.writeframes(s.tobytes())