Draw the STFT of a signal with Python

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Python

signal

I am new to python, and I would like to know how to draw the STFT of a signal with the following program:

import numpy as np
import scipy.signal as sg
import matplotlib.pyplot as plt
from scipy import fftpack

 def _stft(signal, sfreq, fmax):
    n_samp=signal.shape[-1]
    tw = fftpack.fftfreq(n_samp, 1. / sfreq) / n_samp
    tw = np.r_[tw[:1], tw[1:][::-1]]
    Pas=int(fmax*n_samp/sfreq);
    
    STFT = np.empty((n_samp, len(tw)), dtype=np.complex128)
    
    Fx = fftpack.fft(signal)
    XF = np.concatenate([Fx, Fx], axis=-1)
    k = 0.2  # 1 for classical stowckwell transform
    f_range = np.arange(0, Pas-1, 1)
    windows = np.empty(n_samp)
    for i_f in f_range:
        if i_f == 0.:
            window = np.ones(n_samp)
        else:
            f=i_f
            window = ((f / (np.sqrt(2. * np.pi) * k)) *
                      np.exp(-0.5 * (1. / k ** 2.) * (f ** 2.) * tw ** 2.))
            window /= window.sum()  # normalisation
            windows = fftpack.fft(window)
            STFT[..., i_f, :] = fftpack.ifft(XF[..., i_f:i_f + n_samp] * window)
    return STFT 

• Calculate the STFT of a signal with a chirp :

t=np.arange(0,1,Te , dtype=np.float64`
F1 = 50; F2 = 100;

Fe= 1000

chirp1 = np.cos(2*np.pi*(F1*t+((F2-F1)/2)*t**2))

• Display the STFT matrix modulus using the function.

thanking you in advance

What I have tried:

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