How to Validating Entry Widget ? Python

For validating the data You can place a text validation function with the Add Record button callback, so that when the user clicks the add record it first checks each entry field to make sure that certain criteria are met.

For example, I added a validate_text function that is called on each entry widgets text when the add record button is clicked. It first makes sure the entry isn't left blank, then it checks for numbers only for the age and numbers field, and then checks the rest to make sure there are no numbers in the text. If any of the conditions are true then it shows an error messagebox and no record is added to the main_lst or the csv file. Otherwise it adds the record to the main_lst and to the gui.

import csv
from tkinter import *
from tkinter import messagebox

def load_data(path):      # Load data from csv file at program start.
    reader = csv.reader(open(path))
    return list(reader)[1:]

window=Tk()
window.geometry("800x500+0+0")
window.title("Employee Management System")
window.maxsize(width=800,height=500)
window.minsize(width=800,height=500)
FILEPATH = 'data.csv'

main_lst = load_data(FILEPATH)  # Load csv data into `main_lst`


def view():
  index = listbox1.curselection()[0]
  NameLabel2.config(text=main_lst[index][0])
  AgeLabel2.config(text=main_lst[index][1])
  GenderLabel2.config(text=main_lst[index][2])
  PositionLabel2.config(text=main_lst[index][3])
  AddressLabel2.config(text=main_lst[index][4])

def OpenFile():
    pass


def validate_text(field, text):
    if not text:
        messagebox.showinfo("Invalid Entry","Values cannot be left blank.")
        return False
    elif field in ["number", "age"]:
        if not text.isnumeric():
            messagebox.showinfo("Invalid Entry", f"{field.title()} must be numeric.")
            return False
    elif not all([not i.isdigit() for i in text]):
        messagebox.showinfo("Invalid Entry", f"Numbers not permitted in {field.title()} field.")
        return False
    return True

def Add():
    entries = {"name": Nametxt, "age": Agetxt, "gender": Gendertxt, "position": Positiontxt, "number": Numbertxt,"address": Addresstxt}
    values = []
    for key, val in entries.items():
        text = val.get()
        if not validate_text(key, text):
            return
        values.append(text)
    main_lst.append(values)
    listbox1.insert(len(List_of_Name), values[0])  # add it to the listbox list
    List_of_Name.append(values[0])  # store it in the list of names
    messagebox.showinfo("Information","The data has been added successfully")

def Save():
   with open(FILEPATH,"w") as file:
      writer = csv.writer(file, lineterminator='\n')
      writer.writerow(["Fullname","Age","Gender","Position","Phone Number","Address"])
      writer.writerows(main_lst)  #  now when it writes to file it will contain all the data.
      messagebox.showinfo("Information","Saved succesfully")

def Clear():
   Nametxt.delete(0,END)
   Agetxt.delete(0,END)
   Gendertxt.delete(0,END)
   Positiontxt.delete(0,END)
   Numbertxt.delete(0,END)
   Addresstxt.delete(0,END)

def Exit():
    wayOut = messagebox.askyesno("Employee Management System", "Do you want to exit the system")
    if wayOut > 0:
        Save()  # Added a call to save upon exiting.
        window.destroy()
        return

List_of_Name=[]
for x in list(range(0,len(main_lst))):
    List_of_Name.append(main_lst[x][0])

var = StringVar(value=List_of_Name)
listbox1 = Listbox(window, listvariable=var)
listbox1.grid(row=3,column=0)

buttonView = Button(text="ViewRecord", padx=10, pady=4, bd=4,
                    font=('ariel',12,'bold'), width=8, fg='black',
                    bg="dark gray", command=view).grid(row=3,column=1)
NameLabel = Label(window,text="FullName").grid(row=5,column=0,sticky="w")
AgeLabel=Label(window,text="Age").grid(row=6,column=0,sticky="w")
GenderLabel=Label(window,text="Gender").grid(row=7,column=0,sticky="w")
PositionLabel=Label(window,text="Position").grid(row=8,column=0,sticky="w")
AddressLabel=Label(window,text="Address").grid(row=9,column=0,sticky="w")
NameLabel2=Label(window,text="")
NameLabel2.grid(row=5,column=1,sticky="w")
AgeLabel2=Label(window,text="")
AgeLabel2.grid(row=6,column=1,sticky="w")
GenderLabel2=Label(window,text="")
GenderLabel2.grid(row=7,column=1,sticky="w")
PositionLabel2=Label(window,text="")
PositionLabel2.grid(row=8,column=1,sticky="w")
AddressLabel2=Label(window,text="")
AddressLabel2.grid(row=9,column=1,sticky="w")
Namelabel3=Label(window,text="Full Name",
                    font=('arial',12,'bold'),bd=3,fg="white",
                    bg="dark blue",).grid(row=0,column=0,sticky="w")
Nametxt = Entry(window,font=('ariel',12),bd=4,width=22, justify='left')
Nametxt.grid(row=0,column=1)

Agelabel3=Label(window,text="Age",font=("ariel",12,'bold'),bd=3,fg='white',
                bg="dark blue",).grid(row=0,column=2)
Agetxt=Entry(window,font=('ariel',12),bd=4, justify='left')
Agetxt.grid(row=0,column=3)

GenderLabel3=Label(window,text="Gender",font=('ariel',12,'bold'),bd=3,fg='white',
                bg="dark blue").grid(row=1,column=0,sticky="w")
Gendertxt=Entry(window,font=('ariel',12),bd=4, justify='left')
Gendertxt.grid(row=1,column=1)

PositionLabel3=Label(window,text="Position",font=('ariel',12,'bold'),bd=3,fg='white',
                bg="dark blue").grid(row=1,column=2,sticky="w")
Positiontxt=Entry(window,font=('ariel',12),bd=4, justify='left')
Positiontxt.grid(row=1,column=3)

NumberLabel3=Label(window,text="Mob Number",font=('ariel',12,'bold'),bd=3,fg='white',
                bg="dark blue").grid(row=2,column=0,sticky="w")
Numbertxt=Entry(window,font=('ariel',12),bd=4, justify='left')
Numbertxt.grid(row=2,column=1)

AddressLabel3=Label(window,text="Address",font=('ariel',12,'bold'),bd=3,fg='white',
                bg="dark blue").grid(row=2,column=2,sticky="w")
Addresstxt=Entry(window,font=('ariel',12),bd=4, justify='left')
Addresstxt.grid(row=2,column=3)

#  Button
LoadButton=Button(text="Load File", padx=10, pady=4, bd=4, font=('ariel',12,'bold'),
                    width=8,fg='black',bg="dark gray", command=OpenFile).grid(row=3,column=2)
AddButton=Button(text="Add Record", padx=10, pady=4, bd=4, font=('ariel',12,'bold'),
                    width=8,fg='black',bg="dark gray",command=Add).grid(row=3,column=3)
SaveButton=Button(text="Save", padx=10, pady=4, bd=4, font=('ariel',12,'bold'),
                    width=8,fg='black',bg="dark gray",command=Save).grid(row=4,column=1)
ClearButton=Button(text="Clear", padx=10, pady=4, bd=4, font=('ariel',12,'bold'),
                    width=8,fg='black',bg="dark gray",command=Clear).grid(row=4,column=2)
ExitButton=Button(text="Exit", padx=10, pady=4, bd=4, font=('ariel',12,'bold'),
                    width=8,fg='black', bg="dark gray",command=Exit).grid(row=4,column=3)

window.mainloop()