# GUI: Function for the discharge equation by Addition in 1949

I have upgraded my Python code to include a graphical user interface. Here is the code:

Run the program online here: http://www.codeskulptor.org/#user21_ikyPgf2883_1.py

```import simplegui

C,L,H,n=0,0,0,0
C_str, L_str,H_str,n_str='','','',''
result=0
result_str=''

# Handler for mouse click

# Handler to draw on canvas

def enter_C(t):
global C, C_str
C = float(t)
C_str='You have entered C: '+''+ str(C)
print C

def enter_L(t):
global L, L_str
L = float(t)
L_str='You have entered L: '+''+ str(L)
print L

def enter_H(t):
global H, H_str
H = float(t)
H_str='You have entered H: '+''+ str(H)
print H

def enter_n(t):
global n, n_str
n = float(t)
n_str='You have entered n: '+''+ str(n)
print n

def discharge_weir():
#Weirs allow hydrologists and engineers a simple method of measuring
#the volumetric flow rate in small to medium-sized streams
# Function for the discharge equation by Addition in 1949, for TRAPEZOIDAL WEIR
'''
Q is flow rate
C is a constant for structure, when flow in cfs, C=3.37
L is the width of the crest in FEET
H is the height of head of water over the crest in FEET
n varies with structure (e.g. 3/2 for horizontal weir, 5/2 for v-notch weir)
'''
global C,L,H,n, result, result_str
result=round(C*L*(H**n),2)
print result
result_str=str(result)+ ' is the flow in CFS using Addition (1949) formula'

def draw_handler(canvas):
canvas.draw_text(C_str, [50,22], 20, "White")
canvas.draw_text(L_str, [50,52], 20, "White")
canvas.draw_text(H_str, [50,82], 20, "White")
canvas.draw_text(n_str, [50,112], 20, "White")
canvas.draw_text(result_str, [50,142], 20, "White")
#canvas.draw_text(result_str, [50,152], 24, "White")

# Create a frame and assign callbacks to event handlers
frame = simplegui.create_frame("Calculate Flow in CFS based on Addition Formula", 500, 400,400)
label = frame.add_label('Calculate Flow in CFS from Weirs:')
labe2 = frame.add_label('By Ankan Basu, CPG')