Text editor with Tkinter Python 3

I am trying to build a text editor with different tabs, and each one is a file, but the problem is that when I try to save the file, it doesn't read nothing, it creates a new file with no content. Before I didn't have the Tab class and it worked, but the problem was that it saved all the files with the same content.

Here is the code:

from tkinter import *
from tkinter import filedialog, ttk
import os

class App():
    def __init__(self):

    title = 'New document'
    self.root = Tk()
    self.root.geometry('300x200')
    self.root.iconbitmap('icon.ico')
    self.root.title(title)


    self.tabs = {'ky': 0}
    self.notebook = ttk.Notebook(self.root)
    self.notebook.pack(expand = True, fill= 'both')


    menubar = Menu(self.root)
    # create a pulldown menu, and add it to the menu bar
    filemenu = Menu(menubar, tearoff=0)
    filemenu.add_command(label="New...", command=self.generate_tab)
    filemenu.add_command(label="Open", command = self.open_file)
    filemenu.add_command(label="Save", command= self.save_file)
    filemenu.add_separator()
    filemenu.add_command(label="Exit", command= self.root.quit)
    menubar.add_cascade(label="File", menu = filemenu)

    editmenu = Menu(menubar, tearoff=0)
    editmenu.add_command(label="Undo")
    editmenu.add_command(label="Redo")
    editmenu.add_separator()
    menubar.add_cascade(label="Edit", menu=editmenu)
    self.root.config(menu=menubar)

def open_file(self):
    file = open(filedialog.askopenfilename(), 'r+')
    text_value = file.read()
    self.textWidget.delete(1.0, "end-1c")
    self.textWidget.insert("end-1c", text_value)
    title = os.path.basename(file.name)
    self.root.title(title)
    file.close()

def add_tab(self, name):
    tab = Tab(self.notebook, name)
    print(name)
    self.notebook.add(tab, text=name)

def save_file(self):
    self.get_tab().save_tab()

def get_tab(self):
    tab = Tab(self.notebook, 'Document ' + str(self.notebook.index('current')))
    return tab

def generate_tab(self):
    if self.tabs['ky'] < 20:
        self.tabs['ky'] += 1
        self.add_tab('Document ' + str(self.tabs['ky']))

def run(self):
    self.root.mainloop()

class Tab(Frame):

def __init__(self, root, name):
    Frame.__init__(self, root)

    self.root = root
    self.name = name

    self.textWidget = Text(self)
    self.textWidget.pack(expand=True, fill='both')

def save_tab(self):
    print(self.textWidget.get("1.0", 'end-1c'))
    file = open(filedialog.asksaveasfilename() + '.txt', 'w+')
    file.write(self.textWidget.get("1.0", 'end-1c'))
    print(os.path.basename(file.name))
    #title = os.path.basename(file.name)
    file.close()



if __name__ == '__main__':
    app1 = App()
    app1.run()

Problem lies with your get_tab method. It doesn't actually return the object that represents the currently open tab. It returns a new tab that has no content.

In order to fix your problem you need to keep a record of the tabs you've created. I've created a 'workable' version that adds the object of each tab to a list when they are created. This way if you are currently in "Document 3" and press save, it will get the Tab object that relates to document 3.

from tkinter import *
from tkinter import filedialog, ttk
import os

class App():
    def __init__(self):

        title = 'New document'
        self.root = Tk()
        self.root.geometry('300x200')
        #self.root.iconbitmap('icon.ico')
        self.root.title(title)


        self.tabs = {'ky': 0}
        #Keep a record of the open tabs in a list.
        self.tab_list = []
        self.notebook = ttk.Notebook(self.root)
        self.notebook.pack(expand = True, fill= 'both')


        menubar = Menu(self.root)
        # create a pulldown menu, and add it to the menu bar
        filemenu = Menu(menubar, tearoff=0)
        filemenu.add_command(label="New...", command=self.generate_tab)
        filemenu.add_command(label="Open", command = self.open_file)
        filemenu.add_command(label="Save", command= self.save_file)
        filemenu.add_separator()
        filemenu.add_command(label="Exit", command= self.root.quit)
        menubar.add_cascade(label="File", menu = filemenu)

        editmenu = Menu(menubar, tearoff=0)
        editmenu.add_command(label="Undo")
        editmenu.add_command(label="Redo")
        editmenu.add_separator()
        menubar.add_cascade(label="Edit", menu=editmenu)
        self.root.config(menu=menubar)

    def open_file(self):
        file = open(filedialog.askopenfilename(), 'r+')
        text_value = file.read()
        self.textWidget.delete(1.0, "end-1c")
        self.textWidget.insert("end-1c", text_value)
        title = os.path.basename(file.name)
        self.root.title(title)
        file.close()

    def add_tab(self, name):
        tab = Tab(self.notebook, name)
        print(name)
        self.notebook.add(tab, text=name)
        self.tab_list.append(tab)

    def save_file(self):
        tab_to_save = self.get_tab()
        print(tab_to_save)
        tab_to_save.save_tab()

    def get_tab(self):
        print(self.notebook.index('current'))
        #Get the tab object from the tab_list based on the index of the currently selected tab
        tab = self.tab_list[self.notebook.index('current')]
        return tab

    def generate_tab(self):
        if self.tabs['ky'] < 20:
            self.tabs['ky'] += 1
            self.add_tab('Document ' + str(self.tabs['ky']))

    def run(self):
        self.root.mainloop()

class Tab(Frame):

    def __init__(self, root, name):
        Frame.__init__(self, root)

        self.root = root
        self.name = name

        self.textWidget = Text(self)
        self.textWidget.pack(expand=True, fill='both')

    def save_tab(self):
        print(self.textWidget.get("1.0", 'end-1c'))
        file = open(filedialog.asksaveasfilename() + '.txt', 'w+')
        file.write(self.textWidget.get("1.0", 'end-1c'))
        print(os.path.basename(file.name))
        #title = os.path.basename(file.name)
        file.close()



if __name__ == '__main__':
    app1 = App()
    app1.run()