Error: Attribute error in TCL - python-3.x

Question

I am trying to create an application in Python GUI using tkinter. Here is the code I'm using for the GUI part. Whenever I try to access my Entry Widget I get error.
Ex:Sin_put.get() should give me the text in the Entry widget but it gives me an error
AttributeError: 'NoneType' object has no attribute 'get'
I'm relatively new to Python. So if you guys have any suggestions to improve the functionality you're most welcome.
from tkinter import *
from tkinter import ttk
sys.path.insert(0, 'home/ashwin/')
import portscanner
class App:
def __init__(self, master):
master.option_add('*tearOff', False)
master.resizable(False,False)
self.nb = ttk.Notebook(master)
self.nb.pack()
self.nb.config(width=720,height=480)
self.zipframe = ttk.Frame(self.nb)
self.scanframe = ttk.Frame(self.nb)
self.botframe = ttk.Frame(self.nb)
self.mb = Menu(master)
master.config(menu = self.mb)
file = Menu(self.mb)
info = Menu(self.mb)
self.mb.add_cascade(menu = file, label = 'Tools')
self.mb.add_cascade(menu = info, label = 'Help')
file.add_command(label='Zip Cracker', command = self.zipframe_create)
file.add_command(label='Port Scanner', command = self.scanframe_create)
file.add_command(label='Bot net', command =self.botframe_create)
info.add_command(label='Usage', command=(lambda:print('Usage')))
info.add_command(label='About', command=(lambda:print('About')))
def zipframe_create(self):
self.nb.add(self.zipframe,text='Zip')
self.zipframe.config(height=480,width=720)
zlabel1 = ttk.Label(self.zipframe, text='Select the zip file').grid(row=0,column=0, padx=5, pady=10)
zlabel2 = ttk.Label(self.zipframe, text='Select the dictionary file').grid(row=2,column=0, padx=5)
ztext1 = ttk.Entry(self.zipframe, width = 50).grid(row=0,column=1,padx=5,pady=10)
ztext2 = ttk.Entry(self.zipframe, width = 50).grid(row=2,column=1,padx=5)
zoutput = Text(self.zipframe, width=80, height=20).grid(row=3,column=0,columnspan = 3,padx=5,pady=10)
zb1 = ttk.Button(self.zipframe, text='Crack', width=10).grid(row=0,column=2,padx=5,pady=10)
def scanframe_create(self):
self.nb.add(self.scanframe,text='Scan')
self.scanframe.config(height=480,width=720)
slabel1 = ttk.Label(self.scanframe, text='IP address').grid(row=0,column=0, padx=5, pady=10)
sin_put = ttk.Entry(self.scanframe, width = 50).grid(row=0,column=1,padx=5,pady=10)
soutput = Text(self.scanframe, width=80, height=20).grid(row=3,column=0,columnspan = 3,padx=5,pady=10)
sb1 = ttk.Button(self.scanframe, text='Scan', width=6,command= print('Content: {}'.format(sin_put.get()))).grid(row=0,column=2,padx=5,pady=10)
def botframe_create(self):
self.nb.add(self.botframe,text='Bot')
self.botframe.config(height=480,width=720)
blabel1 = ttk.Label(self.botframe, text='IP address').grid(row=0,column=0, padx=5, pady=10)
blabel2 = ttk.Label(self.botframe, text='Username').grid(row=1,column=0, padx=2)
blabel3 = ttk.Label(self.botframe, text='password').grid(row=2,column=0, padx=2)
btext1 = ttk.Entry(self.botframe, width = 30).grid(row=0,column=1,padx=5,pady=10)
btext2 = ttk.Entry(self.botframe, width = 30).grid(row=1,column=1)
btext2 = ttk.Entry(self.botframe, width = 30).grid(row=2,column=1)
boutput = Text(self.botframe, width=80, height=20).grid(row=3,column=0,columnspan = 3,padx=5,pady=10)
bb1 = ttk.Button(self.botframe, text='Connect', width=8).grid(row=2,column=2,padx=5,pady=10)
def main():
root = Tk()
feedback = App(root)
root.mainloop()
if __name__ == "__main__": main()

Answer 1

grid() returns None so sin_put will always equal None. Instead of passing the Tkinter ID to grid() you have to store it first if you want to reference it later. Note that for the Buttons, putting it all on one line is fine as you don't use the button's ID later.
sin_put=ttk.Entry(self.scanframe, width = 50) ## stores the return ID from Entry
sin_put.grid(row=0,column=1,padx=5,pady=10) ## don't catch return from grid as it is None