I am a beginner of Tkinter and i am trying to understand how open a new window to compute some variables.
In this example a first window ("input") with a button appears. After press the "start" a new window is create where i can import a Circumference value to convert in a diameter pressing the button "convert".
when i press this buttom an error appears in the console:
Exception in Tkinter callback
Traceback (most recent call last):
File "C:\Python27\lib\lib-tk\Tkinter.py", line 1470, in __call__
return self.func(*args)
File "C:/Users/samsung/PycharmProjects/test_FirstDensity/openANDread.py", line 55, in convert
convert = tk.Button(c2d, text="Convert", command=convert_c2d, activeforeground="red")
UnboundLocalError: local variable 'convert_c2d' referenced before assignment
I tried several solutions without resolving my problem.
my code is:
from __future__ import division
from Tkinter import *
from math import pi
import tkMessageBox
import Tkinter, Tkconstants, tkFileDialog
from numpy import nan
import Tkinter as tk
class MainWindow(Frame):
def __init__(self):
Frame.__init__(self)
self.filename = None
self.master.title("input")
self.master.minsize(250, 150)
self.grid(sticky=E+W+N+S)
top=self.winfo_toplevel()
top.rowconfigure(0, weight=1)
top.columnconfigure(0, weight=1)
for i in range(1): self.rowconfigure(i, weight=1)
self.columnconfigure(1, weight=1)
self.button0 = Button(self, text="start", command=self.convert, activeforeground="red")
self.button0.grid(row=0, column=1, pady=2, padx=2, sticky=E+W+N+S)
def convert(self):
c2d = Tk()
c2d.title("C2DBH converter")
c2d.minsize(350, 150)
c2d.grid()
res = StringVar(c2d)
res.set("---")
for i in range(3): c2d.rowconfigure(i, weight=1)
c2d.columnconfigure(1, weight=1)
label_c = tk.Label(c2d, text='Circumference')
label_c.grid(row=0, column=0, padx=2, sticky=E+W+N+S)
entry_c = Entry(c2d)
entry_c.grid(row=0, column=1, padx=2,sticky=E+W+N+S)
label_d = tk.Label(c2d, text='Diameter')
label_d.grid(row=1, column=0, padx=2, sticky=E+W+N+S)
result = tk.Label(c2d, textvariable=res, fg="red")
result.grid(row=1, column=1, pady=2, padx=2, sticky=E+W+N+S)
convert = tk.Button(c2d, text="Convert", command=convert_c2d, activeforeground="red")
convert.grid(row=2, column=0, columnspan=2, pady=2, padx=2, sticky=E+W+N+S)
def convert_c2d(n):
if not n.get():
return res.set("Insert a numeric value.")
try:
c = float(n.get())
diameter = c/pi
return res.set(str(diameter))
except ValueError:
return res.set("Insert a numeric value.")
You should define the function before you reference it.
>>> def f():
... convert_c2d(1)
... def convert_c2d(n):
... pass
...
>>> f()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 2, in f
UnboundLocalError: local variable 'convert_c2d' referenced before assignment
>>> def g():
... def convert_c2d(n):
... pass
... convert_c2d(1)
...
>>> g()
>>>
Simply change of the codes as below will solve your problem:
def convert_c2d(n):
if not n.get():
return res.set("Insert a numeric value.")
try:
c = float(n.get())
diameter = c/pi
return res.set(str(diameter))
except ValueError:
return res.set("Insert a numeric value.")
convert = tk.Button(c2d, text="Convert", command=convert_c2d, activeforeground="red")
convert.grid(row=2, column=0, columnspan=2, pady=2, padx=2, sticky=E+W+N+S)
UPDATE
convert_c2d
takes a parameter. But tkinter does not call the command callback with argument. You should pass it using another function (or lambda as below):
convert = tk.Button(c2d, text="Convert", command=lambda: convert_c2d(entry_c),
activeforeground="red")
or you can change the convert_c2d
not to take any argument, and make the function directly access entry_c
. (nested function can access the variable from enclosing scope).
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