Checking if the user presses 'Return' while selected in an Entry box Tkinter

Question

I'm using Tkinter to create a GUI for a simple geometry calculator I'm creating.

Basically, what I have is an Entry box. What I want is for the program/GUI/system to detect when the user of the program hits the 'Enter' or 'return' key WHILE they are in the Entry box. When this is detected, I want the contents of the Entry box to be appended to a list I have defined earlier. I also want a simple label to be created on the GUI that displays the contents of the list (including the appended item(s)). Note that the list begins with nothing in it.

Here is my code so far:

from tkinter import *
#Window setup(ignore this)
app = Tk()
app.title('Geometry Calculator')
app.geometry('384x192+491+216')
app.iconbitmap('Geo.ico')
app.minsize(width=256, height=96)
app.maxsize(width=384, height=192)
app.configure(bg='WhiteSmoke')
#This is the emtry list...
PointList = []
#Here is where I define the variable that I will be appending to the list (which is the              object of the Entry box below)
StrPoint = StringVar()
def list_add(event):
#I don't really know how the bind-checking works and how I would implement it; I want to check if the user hits enter while in the Entry box here
    if event.char == '':
        PointList.append(StrPoint)
e1 = Entry(textvariable=StrPoint).grid(row=0, column=0)
app.bind('<Return>', list_add)

mainloop()

I don't really know the proper way to check for 'Return' and then use it in an if statement. I hope you understand what I'm trying to get help with, and I've looked all around for an explanation that I could understand with no success.

Answer 1

Instead of binding with the app just bind it with the Entry widget object,i.e,e1

from tkinter import *
#Window setup(ignore this)
app = Tk()
app.title('Geometry Calculator')
app.geometry('384x192+491+216')
app.iconbitmap('Geo.ico')
app.minsize(width=256, height=96)
app.maxsize(width=384, height=192)
app.configure(bg='WhiteSmoke')
#This is the emtry list...
PointList = []
#Here is where I define the variable that I will be appending to the list (which is the              object of the Entry box below)
StrPoint = StringVar()
def list_add(event):
    print ("hello")
#I don't really know how the bind-checking works and how I would implement it; I want to check if the user hits enter while in the Entry box here
    if event.char == '':
        PointList.append(StrPoint)
e1 = Entry(textvariable=StrPoint)
e1.grid(row=0, column=0)#use grid in next line,else it would return None
e1.bind('<Return>', list_add)# bind Entry

mainloop()