The program does not stop at the function (while true loop) in Python

Question

this is my first time asking question in this forum. If there are mistakes in posting this question, please mention it.

I am doing a menu function by using Python. In the code, I used def to classify the functions like keypad and what to display. The following is the code:

#import
import RPi.GPIO as GPIO
import time

def main():    
  # Initialise display
  lcd_init()
  definition()
  while True:
        lcd_string("Press any key to",LCD_LINE_1)
        lcd_string("continue",LCD_LINE_2)
        keypad_init()
        key_pad()
        time.sleep(0.5)
        menu_page()
        key_pad1()
        time.sleep(0.5)

def keypad_init():
  for j in range(4):
        GPIO.setup(col[j],GPIO.OUT)
        GPIO.output(col[j],1)

  for i in range(4):
        GPIO.setup(row[i], GPIO.IN, pull_up_down = GPIO.PUD_UP)

def definition():
  global row
  row=[2,3,4,17]
  global col
  col=[27,22,10,9]
  global MATRIX
  MATRIX=[[1,2,3,'A'],
        [4,5,6,'B'],
        [7,8,9,'C'],
        ['Yes',0,'No','D']]
def key_pad():
  # Keypad Function
  while True:
        for j in range(4):
                GPIO.output(col[j],0)
                for i in range(4):
                        if GPIO.input(row[i])==0:
                                return
                                while(GPIO.input(row[i])==0):
                                        pass
                GPIO.output(col[j],1)

def key_pad1():
  # Keypad Function
  global pagecount
  while True:
        for j in range(4):
                GPIO.output(col[j],0)
                for i in range(4):
                        if GPIO.input(row[i])==0:
                                pagecount = MATRIX[i][j]
                                return
                                while(GPIO.input(row[i])==0):
                                        pass
                GPIO.output(col[j],1)

def menu_page():
        lcd_string("1.Diagnose",LCD_LINE_1)
        lcd_string("2.BMI Calculator",LCD_LINE_2)

def option_choose():
  if pagecount ==1:
        lcd_string("Diagnose Start!",LCD_LINE_1)
        lcd_string(" ",LCD_LINE_2)
  if pagecount ==2:
        lcd_string("BMI Calculate!",LCD_LINE_1)
        lcd_string(" ",LCD_LINE_2)

def lcd_init():
  # Initialise display

The problem is that the program does not stop at key_pad() and key_pad1(). It just keep on looping and change the things to be displayed. I want to display "Press any key to continue" until a key is pressed. Please help me with the problem. If the question is not clear, please state them. Thank you very much. Ps. I am using Raspberry Pi for the hardware part

Answer 1

Instead of using a while True loop to wait a key press, you can use GPIO.add_event_detect method :

def keypad_init():
    for j in range(4):
        GPIO.setup(col[j],GPIO.OUT)
        GPIO.output(col[j],1)

    for i in range(4):
        GPIO.setup(row[i], GPIO.IN, pull_up_down = GPIO.PUD_UP)
        GPIO.add_event_detect(row[i], GPIO.BOTH, callback=keyPressed)

def keyPressed:
    # Do your action here

You can also use GPIO.event_detected() method, depending on what you want to do. Take a look at https://sourceforge.net/p/raspberry-gpio-python/wiki/Inputs/