Bit of python help

Question

I've tried to get this to work, but it just freezes. It should display a pyramid, but all it does is.. halts.

from graphics import * 
valid_colours = ['red', 'blue', 'yellow', 'green']
colour = ['', '', '']
while True:
 colour[0] = raw_input("Enter your first colour: ")
 colour[1] = raw_input("Enter your second colour: ")
 colour[2] = raw_input("Enter your third colour: ")
 if ((colour[0] and colour[1] and colour[2]) in valid_colours):
 break 
while True:
 width = raw_input("Enter a width between 2-7: ")
 if width.isdigit(): 
 if (int(width) <= 7 and int(width) >= 2):
 break 
width = int(width)
win = GraphWin("My Mini Project ", 1000, 1000) # 1000 \ 20 = 50
win.setCoords(0 , 0 , 20, 20)
p1 = [0, 2]
while width > 0:
 p = [1, 3]
 loopWidth = 0
 while loopWidth < width:
 loopWidth = loopWidth + 1
 c = 0
 while c <= 10:
 c = c + 1
 if c % 2: 
 colour = "white"
 else:
 colour = "red"
 rectangle = Rectangle(Point(p[0],p1[0]), Point(p[1], p1[1]))
 rectangle.setFill(colour)
 rectangle.setOutline("black")
 rectangle.draw(win)
 p[0] = p[0] + 0.2
 p1[0] = p1[0] + 0.2
 p[0] = p[0] - 2
 p1[0] = p1[0] - 2
 p[0] = p[0] + 2
 p[1] = p[1] + 2
 width = width - 1
 p1[0] = p1[0] + 2
 p1[1] = p1[1] + 2

• o0'.: (1) should post this to stackoverflow, (2) should narrow down the problem, nobody wants to do your work: they might help but you need to put in some effort
• SilentGhost: oh dear, what is it with while loops?
• yarmiganosca: 1st: have you tried stepping through it in pdb or another debugger? have you tried debugging via print statements? 2nd: I'm going to introduce you to some friends of mine (2 in particular): for in loops (the loop around c in particular), and the += and -= assignment operators. They're very helpful and they don't bite.

Answer 1

• Well first the color-input loop does not do what you want it to do.

The 'and' in if ((colour[0] and colour[1] and colour[2]) in valid_colours): compares their string values to each other, where any non-empty string evaluates as True. The expression evaluates to colour[2], assuming it is the last non-empty string, you can prove this with: print (colour[0] and colour[1] and colour[2])

Change to: if (colour[0] in valid_colours and colour[1] in valid_colours and colour[2] in valid_colours):

• Your main rectangle-drawing loop: The intent of the following code is to iterate from 1..width (inclusively)

:

barloopWidth = 0
while loopWidth < width:
 loopWidth = loopWidth + 1
 do stuff using (loopWidth + 1)

so replace it with: for loopWidth in range(1,width+1):

• The loop iterating c and colour through 6 loops of white,red can be rewritten using '*' (the sequence replication operator):

  for colour in ['white','red']*6:

So your main loop becomes:

while width > 0:
 p = [1, 3]
 for loopWidth in range(1,width+1):
 for colour in ['white','red']*6:
 #Draw your rectangles
 p[0] += 2
 p1[0] += 2
 p[0] -= 2
 p1[0] -= 2
 p[0] = p[0] + 2
 p[1] = p[1] + 2
 width = width - 1
 p1[0] += 2
 p1[1] += 2

• As to why it hangs on your pyramid coordinates loop, debug it yourself using print: print 'Drawing rectangle from (%d,%d) to (%d,%d)'% (p[0],p1[0],p[1],p1[1])

You might find it helpful for testing to isolate that code info a function draw_pyramid(), away from get_colors().