Login Application and Validating info using Kivy GUI and Pandas in Python

Prerequisites : Kivy, Pandas

Kivy is a multiplatform GUI library, known for being responsive. It provides management of multiple screens in a single application. 

In this application we will be using multiple screens to log in user’s info and validate it. We will save the information in a csv file and use pandas to validate the information inside of the csv file by reading it into a DataFrame. To build the GUI we will use .kv file.  

Approach :

1. There will be three screens, one for letting the user log in, second for signing up and third for telling if the login was successful.
2. The info will be stored in a csv file.
3. Pandas Library will be used to read the csv file into a DataFrame and further check if the user info already exists or not.
4. If the information entered is invalid, popups will inform the user.
5. Finally, the user will be informed if the login was successful or not.
   

Main program :

# import all the relevant classes
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty
from kivy.lang import Builder
from kivy.uix.popup import Popup
from kivy.uix.floatlayout import FloatLayout
import pandas as pd

# class to call the popup function
class PopupWindow(Widget):
    def btn(self):
        popFun()

# class to build GUI for a popup window
class P(FloatLayout):
    pass

# function that displays the content
def popFun():
    show = P()
    window = Popup(title = "popup", content = show,
                   size_hint = (None, None), size = (300, 300))
    window.open()

# class to accept user info and validate it
class loginWindow(Screen):
    email = ObjectProperty(None)
    pwd = ObjectProperty(None)
    def validate(self):

        # validating if the email already exists
        if self.email.text not in users['Email'].unique():
            popFun()
        else:

            # switching the current screen to display validation result
            sm.current = 'logdata'

            # reset TextInput widget
            self.email.text = ""
            self.pwd.text = ""


# class to accept sign up info
class signupWindow(Screen):
    name2 = ObjectProperty(None)
    email = ObjectProperty(None)
    pwd = ObjectProperty(None)
    def signupbtn(self):

        # creating a DataFrame of the info
        user = pd.DataFrame([[self.name2.text, self.email.text, self.pwd.text]],
                            columns = ['Name', 'Email', 'Password'])
        if self.email.text != "":
            if self.email.text not in users['Email'].unique():

                # if email does not exist already then append to the csv file
                # change current screen to log in the user now
                user.to_csv('login.csv', mode = 'a', header = False, index = False)
                sm.current = 'login'
                self.name2.text = ""
                self.email.text = ""
                self.pwd.text = ""
        else:
            # if values are empty or invalid show pop up
            popFun()

# class to display validation result
class logDataWindow(Screen):
    pass

# class for managing screens
class windowManager(ScreenManager):
    pass

# kv file
kv = Builder.load_file('login.kv')
sm = windowManager()

# reading all the data stored
users=pd.read_csv('login.csv')

# adding screens
sm.add_widget(loginWindow(name='login'))
sm.add_widget(signupWindow(name='signup'))
sm.add_widget(logDataWindow(name='logdata'))

# class that builds gui
class loginMain(App):
    def build(self):
        return sm

# driver function
if __name__=="__main__":
    loginMain().run()

.kv file : .kv file contains all the code to design and place the GUI and to define the direction of the transitions of the screens. 

# there are three screens
windowManager:
    loginWindow:
    signupWindow:
    logDataWindow:

# GUI for the login window
<loginWindow>:
    email : email
    pwd : pwd
    FloatLayout:
        size: root.width, root.height
        Label:
            text : "EMAIL: "
            size_hint : 0.2, 0.1
            pos_hint : {"x":0.25, "top":0.9}
        TextInput:
            id : email
            multiline :False
            size_hint : 0.3, 0.1
            pos_hint : {"x" : 0.45, "top" : 0.9}
        Label:
            text : "PASSWORD: "
            size_hint : 0.2, 0.1
            pos_hint : {"x" : 0.25, "top" : 0.7}
        TextInput:
            id : pwd
            multiline :False
            size_hint : 0.3, 0.1
            pos_hint : {"x" : 0.45, "top" : 0.7}
        Button:
            text : "Create an account"
            size_hint : 0.4, 0.1
            pos_hint : {"x" : 0.33, "top" : 0.4}
            on_release:
                app.root.current = 'signup'
                root.manager.transition.direction = "left"
        Button:
            text : "LOGIN"
            size_hint : 0.3, 0.1
            pos_hint : {"x" : 0.39, "top" : 0.2}
            on_release:
                root.validate()
                root.manager.transition.direction = "up"

# GUI for the signup window
<signupWindow>:
    name2 : name2
    email : email
    pwd : pwd
    FloatLayout:
        Label:
            text : "NAME: "
            size_hint : 0.2, 0.1
            pos_hint : {"x":0.25, "top":0.9}
        TextInput:
            id : name2
            multiline : False
            size_hint : 0.3, 0.1
            pos_hint : {"x" : 0.45, "top" : 0.9}
        Label:
            text : "EMAIL: "
            size_hint : 0.2, 0.1
            pos_hint : {"x" : 0.25, "top" : 0.7}
        TextInput:
            id : email
            multiline : False
            size_hint : 0.3, 0.1
            pos_hint : {"x" : 0.45, "top" : 0.7}
        Label:
            text : "PASSWORD: "
            size_hint : 0.2, 0.1
            pos_hint : {"x" : 0.25, "top" : 0.5}
        TextInput:
            id : pwd
            multiline : False
            size_hint : 0.3, 0.1
            pos_hint : {"x" : 0.45, "top" : 0.5}
        Button:
            text : "SUBMIT"
            size_hint : 0.3, 0.1
            pos_hint : {"x" : 0.39, "top" : 0.28}
            on_press :
                root.signupbtn()
                root.manager.transition.direction = "right"

# GUI to show validation result
<logDataWindow>:
    info : info
    FloatLayout:
        Label:
            id : info
            size_hint : 0.8, 0.2
            pos_hint : {"x" : 0.15, "top" : 0.8}
            text : "SUCCESSFULLY LOGGED IN"
        Button:
            text : "Login"
            size_hint : 0.4, 0.1
            pos_hint : {"x" : 0.33, "top" : 0.55}
            on_release:
                app.root.current = 'login'
                root.manager.transition.direction = "down"
        Button:
            text : "Create new account"
            size_hint : 0.4, 0.1
            pos_hint : {"x" : 0.33, "top" : 0.4}
            on_release:
                app.root.current = 'signup'
                root.manager.transition.direction = "down"


# GUI for pop up window
<P>:
    Label:
        text : "Please enter valid information"
        size_hint : 0.2, 0.1
        pos_hint : {"x" : 0.3, "top" : 0.8}

Output:

Signup Window :

Login Window :

Popup Window:

Validation :