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Hi there, Im writing a program that takes a function and makes a plot of it. the program consists of 2 functions and each creates its own GraphWin. However i want to have a mouse click at the end close both windows. So i returned the window from the first function which i thought should allow it to be accessed and the close() method called, but I keep getting the error, "NameError: global name 'graph' is not defined." I am not sure what I am doing wrong because all the rest works fine. Any help would be appreciated and thank you in advance.

This is my code so far

```
from graphics import *
from math import *
def plot_it(x_start, x_end, y_start, y_end, f_of_x):
x_start = float(x_start.getText())
x_end = float(x_end.getText())
y_start = float(y_start.getText())
y_end = float(y_end.getText())
f_of_x = f_of_x.getText()
graph = GraphWin('Plot of f(x)', 400, 400)
graph.setCoords(x_start, y_start, x_end, y_end)
graph.setBackground('white')
N = 101
delta = (x_end - x_start) / (N - 1)
points = []
for i in range(N):
x = x_start + i * delta
y = eval(f_of_x)
p = Point(x, y)
points.append(p)
for q in range(len(points) - 1):
Line(points[q], points[q+1]).draw(graph)
return graph
def main():
win = GraphWin('Control', 400, 400)
win.setCoords(0.0, 0.0, 2.0, 2.0)
win.setBackground('white')
Text(Point(0.25, 1.75), 'X start: ').draw(win)
Text(Point(0.25, 1.5), 'X end: ').draw(win)
Text(Point(1.25, 1.75), 'Y start: ').draw(win)
Text(Point(1.25, 1.5), 'Y end: ').draw(win)
Text(Point(0.40, 0.75), 'F(x): ').draw(win)
x_start = Entry(Point(0.85, 1.75), 10)
x_start.setText('0.0')
x_start.draw(win)
x_end = Entry(Point(0.85, 1.5), 10)
x_end.setText('0.0')
x_end.draw(win)
y_start = Entry(Point(1.75, 1.75), 10)
y_start.setText('0.0')
y_start.draw(win)
y_end = Entry(Point(1.75, 1.5), 10)
y_end.setText('0.0')
y_end.draw(win)
f_of_x = Entry(Point(1.0, 0.75), 20)
f_of_x.setText('Enter a function')
f_of_x.draw(win)
t = Text(Point(1.0, 0.25), 'Plot f(x)')
t.draw(win)
Polygon(Point(0.75, 0.15), Point(0.75, 0.35), Point(1.25, 0.35), Point(1.25, 0.15)).draw(win)
win.getMouse()
plot_it(x_start, x_end, y_start, y_end, f_of_x)
t.setText('Close window')
win.getMouse()
win.close()
graph.close()
main()
```