[FIXED] Matplotlib not showing librosa specshow in custom class constructor

Issue

I have a custom "waveform"-class which I use for tkinter-applications. Due to testing reasons, i would like to see a spectrogram via librosa.display.specshow() without calling any tkinter-app. Sadly, the following code does not produce an output:

from matplotlib.figure import Figure
from matplotlib.pyplot import show

import librosa as lr
import librosa.display as lrd


class waveform():

    def __init__(self, fp):

        self.sig, self.sr = lr.load(fp, sr=None, res_type="polyphase")

        X = lr.stft(self.sig, n_fft=2**13)
        Xdb = lr.amplitude_to_db(abs(X))

        self.figure = Figure(figsize=(10, 8), dpi=80)
        self.ax = self.figure.add_subplot()
        lrd.specshow(Xdb, sr=self.sr, x_axis="time", y_axis="log", ax=self.ax, cmap='viridis')



if __name__ == "__main__":
    wv = waveform("./noise.wav")
    show()

Are calls to matplotlib (which is what specshow is doing in the background) not rendered when inside of a class constructor?

Solution

The problem seems to come from the fact that you use matplotlib.figure which is not managed by pyplot. Changing the import works for me

from matplotlib.pyplot import figure
# instead of from matplotlib.figure import Figure
# ...

class waveform():
        # ...
        self.figure = figure(figsize=(10, 8), dpi=80)
        # (Just replaced Figure by figure)
# The rest is the same

However, I am not sure if it fits with your use case, so probably a good read is: https://matplotlib.org/stable/api/figure_api.html#matplotlib.figure.Figure.show

Answered By - Adam Oudad