如何从另一个类运行函数并使用其变量？

Question

I'm a beginner in Python working on a simple app for our final year project. This is the only part that I can't solve and I would really appreciate your help. I need to take a value from a live updating csv file, fetch the first element and match it with the reference csv. That part is already working. Then I need it to play the corresponding sound as per the playsound. That part is also already working.

However, since it will be situated in a Kivy app, I need to create multiple classes. Some will handle the data processing side and the Kivy part will handle the display part. But my question today focuses on the Python part not in Kivy.

The first class handles the csv, playsound, and numpy matching.

The second class is where I tried to call the functions of the first class to get them running. I also tried to get the where variable present in the first class so that I could use it in an if statement to verify a match and output a text display.

import serial
import sys
import numpy as np
import time
import csv
import os
import string 
import collections
from playsound import playsound
from pathlib import Path
import os, sys



#import keyboard
class Identifier:
    def csvwriter(self): #function for writing csv file
        try:
            ser = serial.Serial('COM10', baudrate=9600)
            ser.flushInput()

            while True:
                ser_bytes = ser.readline()
                print(ser_bytes)
                file = open("letterz5.csv", "a")
                file.write(str(ser_bytes))
                file.close()

         #       if keyboard.is_pressed('esc'):
         #           break;

            ser.close
        except:
            print("Unexpected error:", sys.exc_info()[0])
            print("Unexpected error:", sys.exc_info()[1])
    def fn_voice(self): #function for parsing and comparing csv file.
        count=1
        while (count>0):
            livecsv=np.genfromtxt("lettera.csv", delimiter=",", skip_header=1, filling_values=np.nan, dtype=int, case_sensitive=True, deletechars='', replace_space=' ')
            refcsv=np.genfromtxt("refcsv1.csv", delimiter=",", skip_header=1, filling_values=np.nan, dtype=int, case_sensitive=True, deletechars='', replace_space=' ')
            A=np.array(livecsv)
            B=np.array(refcsv)
            D = B - A[-1]
            match= B[np.abs(D).sum(axis=1).argmin()]
            where=match[0]
            voice=fn_voice(where)
            time.sleep(1)
            count = count + 1
        var=where
        if var==1:
            A=playsound('audio-alphabet/A.wav',True)
            return A
        elif var==2:
            B=playsound('audio-alphabet/B.wav',True)
            return B
        elif var==3:
            C=playsound('audio-alphabet/C.wav',True)
            return C
        elif var==4:
            D=playsound('audio-alphabet/D.wav',True)
            return D
        elif var==5:
            E=playsound('audio-alphabet/E.wav',True)
            return E
        elif var==6:
            F=playsound('audio-alphabet/F.wav',True)
            return F
        elif var==7:
            G=playsound('audio-alphabet/G.wav',True)
            return G
        elif var==8:
            H=playsound('audio-alphabet/H.wav',True)
            return H
        elif var==9:
            I=playsound('audio-alphabet/I.wav',True)
            return I
        elif var==10:
            J=playsound('audio-alphabet/J.wav',True)
            return J
        elif var==11:
            K=playsound('audio-alphabet/K.wav',True)
            return K
        elif var==12:
            L=playsound('audio-alphabet/L.wav',True)
            return L
        elif var==13:
            M=playsound('audio-alphabet/M.wav',True)
            return M
        elif var==14:
            N=playsound('audio-alphabet/N.wav',True)
            return N
        elif var==15:
            O=playsound('audio-alphabet/O.wav',True)
            return O
        elif var==16:
            P=playsound('audio-alphabet/P.wav',True)
            return P
        elif var==17:
            Q=playsound('audio-alphabet/Q.wav',True)
            return Q
        elif var==18:
            R=playsound('audio-alphabet/R.wav',True)
            return R
        elif var==19:
            S=playsound('audio-alphabet/S.wav',True)
            return S
        elif var==20:
            T=playsound('audio-alphabet/T.wav',True)
            return T
        elif var==21:
            U=playsound('audio-alphabet/U.wav',True)
            return U
        elif var==22:
            V=playsound('audio-alphabet/V.wav',True)
            return V
        elif var==23:
            W=playsound('audio-alphabet/W.wav',True)
            return W
        elif var==24:
            X=playsound('audio-alphabet/X.wav',True)
            return X
        elif var==25:
            Y=playsound('audio-alphabet/Y.wav',True)
            return Y
        elif var==26:
            Z=playsound('audio-alphabet/Z.wav',True)
            return Z
        os.system("rm lettera.csv")



class LetterAScreen(Identifier):
    def identity(self): #I tried to call the functions of Identifier class here but they won't run
        fn_voice() #I need the playsound part to only return playsound when the input data is correct
        fn_csvwriter()
        iden=fn_voice().where #I need to get the variable 'where' from fn_voice() but I can't seem to get it
     def verifier(self):
        verify=identity.iden
        if verify == 1:
            print ("correct")
        else:
            print ("incorrect")

How do I go about this? How do I get all of the first class running, and how do I fetch the where variable so that I can use it in the verifier function? Thank you very much.

Answer 1

In python you cannot access variables like you have done with fn_voice().where .

Read up some more on scope at https://pythonspot.com/scope/ .

The solution to your problem will be to assign the where reference (variable) in the class rather than the method.

class Identifier:
    where = None
    def fn_voice(self):
        where = match[0]

Then you will be able to access where like:

Identifier.where

NB. Remember to check if the value of where is None . We can use standard python truth value testing https://docs.python.org/2.4/lib/truth.html .

if Identifier.where:
    #Logic if where is not None.