How do I store a value entered on a Tk entry widget in a variable

Question

To get the pound sign correct a simple encoding task will do the job as python is unable to understand £ but it can understand the Unicode for a pound sign which is 163 (decimal) or A3 in hex:

Label(app, text= u"\xA3" + "20.50", bg="gold", fg="blue").place(x=20,y=50)

To get the value entered in a Tkinter Entry Widget you have to use a method called get() which takes the current value stored in the widget.

for example if I have Entry widget, a helper function and a button which If pressed which prints the data to sys.stdout It would look like this:

def submit_data():
    username = username_entry.get()
    print username

username_entry = Tk.Entry(root)
submit = Tk.Button(root,text='Enter',command=submit_data)

I corrected your program, but since you haven't named widgets appropriately I named them x,y,z, Your entry widgets data are stored on variables : x_data, y_data, z_data. So there are basically 3 Entry Widgets and when you enter some data in them and press the button marks it prints what you had entered for eg: x_data = K DawG , y_data = Answers , z_data = SO

from Tkinter import *
import tkMessageBox

app = Tk()
# Message Window

def messagePop():
    get_data()
    tkMessageBox.showinfo('Results', '100% Very Good')

# Background colour

app.configure(bg='cornflower blue')

COLORS  =['snow', 'ghost white', 'white smoke', 'gainsboro', 'floral white', 'old lace',
    'linen', 'antique white', 'papaya whip', 'blanched almond', 'bisque', 'peach puff',
    'navajo white', 'lemon chiffon', 'mint cream', 'azure', 'alice blue', 'lavender',
    'lavender blush', 'misty rose', 'dark slate gray', 'dim gray', 'slate gray',
    'light slate gray', 'gray', 'light grey', 'midnight blue', 'navy', 'cornflower blue', 'dark slate blue',
    'slate blue', 'medium slate blue', 'light slate blue', 'medium blue', 'royal blue',  'blue',
    'dodger blue', 'deep sky blue', 'sky blue', 'light sky blue', 'steel blue', 'light steel blue',
    'light blue', 'powder blue', 'pale turquoise', 'dark turquoise', 'medium turquoise', 'turquoise',
    'cyan', 'light cyan', 'cadet blue', 'medium aquamarine', 'aquamarine', 'dark green', 'dark olive green',
    'dark sea green', 'sea green', 'medium sea green', 'light sea green', 'pale green', 'spring green',
    'lawn green', 'medium spring green', 'green yellow', 'lime green', 'yellow green',
    'forest green', 'olive drab', 'dark khaki', 'khaki', 'pale goldenrod', 'light goldenrod yellow',
    'light yellow', 'yellow', 'gold', 'light goldenrod', 'goldenrod', 'dark goldenrod', 'rosy brown',
    'indian red', 'saddle brown', 'sandy brown',
    'dark salmon', 'salmon', 'light salmon', 'orange', 'dark orange',
    'coral', 'light coral', 'tomato', 'orange red', 'red', 'hot pink', 'deep pink', 'pink', 'light pink',
    'pale violet red', 'maroon', 'medium violet red', 'violet red',
    'medium orchid', 'dark orchid', 'dark violet', 'blue violet', 'purple', 'medium purple',
    'thistle', 'snow2', 'snow3',
    'snow4', 'seashell2', 'seashell3', 'seashell4', 'AntiqueWhite1', 'AntiqueWhite2',
    'AntiqueWhite3', 'AntiqueWhite4', 'bisque2', 'bisque3', 'bisque4', 'PeachPuff2',
    'PeachPuff3', 'PeachPuff4', 'NavajoWhite2', 'NavajoWhite3', 'NavajoWhite4',
    'LemonChiffon2', 'LemonChiffon3', 'LemonChiffon4', 'cornsilk2', 'cornsilk3',
    'cornsilk4', 'ivory2', 'ivory3', 'ivory4', 'honeydew2', 'honeydew3', 'honeydew4',
    'LavenderBlush2', 'LavenderBlush3', 'LavenderBlush4', 'MistyRose2', 'MistyRose3',
    'MistyRose4', 'azure2', 'azure3', 'azure4', 'SlateBlue1', 'SlateBlue2', 'SlateBlue3',
    'SlateBlue4', 'RoyalBlue1', 'RoyalBlue2', 'RoyalBlue3', 'RoyalBlue4', 'blue2', 'blue4',
    'DodgerBlue2', 'DodgerBlue3', 'DodgerBlue4', 'SteelBlue1', 'SteelBlue2',
    'SteelBlue3', 'SteelBlue4', 'DeepSkyBlue2', 'DeepSkyBlue3', 'DeepSkyBlue4',
    'SkyBlue1', 'SkyBlue2', 'SkyBlue3', 'SkyBlue4', 'LightSkyBlue1', 'LightSkyBlue2',
    'LightSkyBlue3', 'LightSkyBlue4', 'SlateGray1', 'SlateGray2', 'SlateGray3',
    'SlateGray4', 'LightSteelBlue1', 'LightSteelBlue2', 'LightSteelBlue3',
    'LightSteelBlue4', 'LightBlue1', 'LightBlue2', 'LightBlue3', 'LightBlue4',
    'LightCyan2', 'LightCyan3', 'LightCyan4', 'PaleTurquoise1', 'PaleTurquoise2',
    'PaleTurquoise3', 'PaleTurquoise4', 'CadetBlue1', 'CadetBlue2', 'CadetBlue3',
    'CadetBlue4', 'turquoise1', 'turquoise2', 'turquoise3', 'turquoise4', 'cyan2', 'cyan3',
    'cyan4', 'DarkSlateGray1', 'DarkSlateGray2', 'DarkSlateGray3', 'DarkSlateGray4',
    'aquamarine2', 'aquamarine4', 'DarkSeaGreen1', 'DarkSeaGreen2', 'DarkSeaGreen3',
    'DarkSeaGreen4', 'SeaGreen1', 'SeaGreen2', 'SeaGreen3', 'PaleGreen1', 'PaleGreen2',
    'PaleGreen3', 'PaleGreen4', 'SpringGreen2', 'SpringGreen3', 'SpringGreen4',
    'green2', 'green3', 'green4', 'chartreuse2', 'chartreuse3', 'chartreuse4',
    'OliveDrab1', 'OliveDrab2', 'OliveDrab4', 'DarkOliveGreen1', 'DarkOliveGreen2',
    'DarkOliveGreen3', 'DarkOliveGreen4', 'khaki1', 'khaki2', 'khaki3', 'khaki4',
    'LightGoldenrod1', 'LightGoldenrod2', 'LightGoldenrod3', 'LightGoldenrod4',
    'LightYellow2', 'LightYellow3', 'LightYellow4', 'yellow2', 'yellow3', 'yellow4',
    'gold2', 'gold3', 'gold4', 'goldenrod1', 'goldenrod2', 'goldenrod3', 'goldenrod4',
    'DarkGoldenrod1', 'DarkGoldenrod2', 'DarkGoldenrod3', 'DarkGoldenrod4',
    'RosyBrown1', 'RosyBrown2', 'RosyBrown3', 'RosyBrown4', 'IndianRed1', 'IndianRed2',
    'IndianRed3', 'IndianRed4', 'sienna1', 'sienna2', 'sienna3', 'sienna4', 'burlywood1',
    'burlywood2', 'burlywood3', 'burlywood4', 'wheat1', 'wheat2', 'wheat3', 'wheat4', 'tan1',
    'tan2', 'tan4', 'chocolate1', 'chocolate2', 'chocolate3', 'firebrick1', 'firebrick2',
    'firebrick3', 'firebrick4', 'brown1', 'brown2', 'brown3', 'brown4', 'salmon1', 'salmon2',
    'salmon3', 'salmon4', 'LightSalmon2', 'LightSalmon3', 'LightSalmon4', 'orange2',
    'orange3', 'orange4', 'DarkOrange1', 'DarkOrange2', 'DarkOrange3', 'DarkOrange4',
    'coral1', 'coral2', 'coral3', 'coral4', 'tomato2', 'tomato3', 'tomato4', 'OrangeRed2',
    'OrangeRed3', 'OrangeRed4', 'red2', 'red3', 'red4', 'DeepPink2', 'DeepPink3', 'DeepPink4',
    'HotPink1', 'HotPink2', 'HotPink3', 'HotPink4', 'pink1', 'pink2', 'pink3', 'pink4',
    'LightPink1', 'LightPink2', 'LightPink3', 'LightPink4', 'PaleVioletRed1',
    'PaleVioletRed2', 'PaleVioletRed3', 'PaleVioletRed4', 'maroon1', 'maroon2',
    'maroon3', 'maroon4', 'VioletRed1', 'VioletRed2', 'VioletRed3', 'VioletRed4',
    'magenta2', 'magenta3', 'magenta4', 'orchid1', 'orchid2', 'orchid3', 'orchid4', 'plum1',
    'plum2', 'plum3', 'plum4', 'MediumOrchid1', 'MediumOrchid2', 'MediumOrchid3',
    'MediumOrchid4', 'DarkOrchid1', 'DarkOrchid2', 'DarkOrchid3', 'DarkOrchid4',
    'purple1', 'purple2', 'purple3', 'purple4', 'MediumPurple1', 'MediumPurple2',
    'MediumPurple3', 'MediumPurple4', 'thistle1', 'thistle2', 'thistle3', 'thistle4',
    'gray1', 'gray2', 'gray3', 'gray4', 'gray5', 'gray6', 'gray7', 'gray8', 'gray9', 'gray10',
    'gray11', 'gray12', 'gray13', 'gray14', 'gray15', 'gray16', 'gray17', 'gray18', 'gray19',
    'gray20', 'gray21', 'gray22', 'gray23', 'gray24', 'gray25', 'gray26', 'gray27', 'gray28',
    'gray29', 'gray30', 'gray31', 'gray32', 'gray33', 'gray34', 'gray35', 'gray36', 'gray37',
    'gray38', 'gray39', 'gray40', 'gray42', 'gray43', 'gray44', 'gray45', 'gray46', 'gray47',
    'gray48', 'gray49', 'gray50', 'gray51', 'gray52', 'gray53', 'gray54', 'gray55', 'gray56',
    'gray57', 'gray58', 'gray59', 'gray60', 'gray61', 'gray62', 'gray63', 'gray64', 'gray65',
    'gray66', 'gray67', 'gray68', 'gray69', 'gray70', 'gray71', 'gray72', 'gray73', 'gray74',
    'gray75', 'gray76', 'gray77', 'gray78', 'gray79', 'gray80', 'gray81', 'gray82', 'gray83',
    'gray84', 'gray85', 'gray86', 'gray87', 'gray88', 'gray89', 'gray90', 'gray91', 'gray92',
    'gray93', 'gray94', 'gray95', 'gray97', 'gray98', 'gray99']

# The position and size relative to the screen
app.geometry('500x500+450+140')

# The title of the program
app.title('Maths4Primary')

# The icon
app.wm_iconbitmap('MathIcon.ico')

# Object positioning in the program
# def GridPos:

# I might use the place() method for the screen layout.
Label(app, text="Put these prices in order", bg="gold", fg="blue").place(x=100,y=20)
Label(app, text= u"\xA3" + "20.50", bg="gold", fg="blue").place(x=20,y=50)
Label(app, text="Question 3", bg="gold", fg="blue").place(x=20,y=120)

# Entry
def get_data():
    x_data = x.get()
    y_data = y.get()
    z_data = z.get()
    print "x_data = {0} , y_data = {1} , z_data = {2}".format(x_data,y_data,z_data)

x = Entry(app)
y = Entry(app)
z = Entry(app)

x.place(x=150,y=60)
y.place(x=150,y=80)
z.place(x=150,y=100)

# Buttons
B1 = Button(app,text='Marks',bg='gold',fg='blue', command = messagePop ).place(x=425,y=450)

app.mainloop()

Just in case you wanted your data to be integers, use the int() method (you might need a try except block too)

x_data = int(x.get())
y_data = int(y.get())
z_data = int(z.get())