While loop won't end when I tell it!

[lorayyne]

Hello,

I am trying to write a program that flips a coin until it gets the sequence "heads tails heads" and then stops and says how many flips it took to get that sequence. This is what I have so far:

import random
import time
import string

def coinflip():	
	
	heads = 0
	tails = 0
	flips = 0
	hth = "HTH"

	rec = open('cointoss.txt', 'w')

	N = int(raw_input('Welcome to the Coin Toss!  How many times do you want to flip the coin?: '))

	while (flips < N):
		flip = random.randint(1,2)
		if flip == 1:
			heads += 1
			if heads > 0:
				rec.write('H')
				time.sleep(.1)
				file = open('cointoss.txt', 'r')
				text = file.read()
				file.close()
				search = text.find(hth)

				if search == -1:
					flips += 1
				else:
					flips += 1
					print "needed", flips ," flips to get hth."
					flips = N

			
		else:
			tails += 1
			if tails > 0:
				rec.write('T')
				time.sleep(.1)
				file = open('cointoss.txt', 'r')
				text = file.read()
				file.close()
				search = text.find(hth)
				
				if search == -1:
					flips += 1

				else:
					flips += 1
					print "needed", flips ," flips to get hth."
					flips = N


	print "you got", heads ," heads and", tails ," tails."

The way the code is, it runs to for the full N every time regardless of whether the sequence appears before it runs the full number of times. Why doesn't it stop when the HTH sequence appears? Any help is greatly appreciated.

[vegaseat]

For heaven sake do us a favor and don't use tabs for your Python indentations. It makes code look ungainly! Use the standard 4 spaces as recommended in the Python style guide. I would love to highlight and copy your code to paste it into my editor for a quick test, but it gets all screwed up in the process!

The Python style guide by GVR ('Mr. Python') himself:
http://www.python.org/peps/pep-0008.html

Note: The story has it that GVR regretted to even mention tabs!

[lorayyne]

Here:

import random
import time
import string

def coinflip():	
	
    heads = 0
    tails = 0
    flips = 0
    hth = "HTH"

    rec = open('cointoss.txt', 'w')

    N = int(raw_input('Welcome to the Coin Toss!  How many times do you want to flip the coin?: '))

    while (flips < N):
        flip = random.randint(1,2)
        if flip == 1:
            heads += 1
            if heads > 0:
            rec.write('H')
            time.sleep(.1)
            file = open('cointoss.txt', 'r')
            text = file.read()
            file.close()
            search = text.find(hth)

            if search == -1:
                flips += 1
            else:
                flips += 1
                print "needed", flips ," flips to get hth."
                flips = N

			
        else:
            tails += 1
            if tails > 0:
                rec.write('T')
                time.sleep(.1)
                file = open('cointoss.txt', 'r')
                text = file.read()
                file.close()
                search = text.find(hth)
				
                if search == -1:
                    flips += 1

                else:
                    flips += 1
                    print "needed", flips ," flips to get hth."
                    flips = N


    print "you got", heads ," heads and", tails ," tails."

[vegaseat]

Your program does not work since you are trying to write to and read from the file at the same time. Store your temporary results in a string and then write to the file at the end ...

import random
import time

def coinflip():
    """flip the coin until you get an HTH pattern"""
    heads = 0
    tails = 0
    flips = 0
    hth = "HTH"

    # might be easier to set N to something like 50
    N = int(raw_input('Welcome to the Coin Toss!  '\
        'How many times do you want to flip the coin?: '))
    # optional, make sure N is large enough
    if N < 20:
        N = 20

    # create an empty string
    text = ""
    while (flips < N):
        flip = random.randint(1, 2)
        if flip == 1:
            heads += 1
            if heads > 0:
                text += 'H'
                time.sleep(.1)
                search = text.find(hth)
                #print flip, text, search  # testing
        else:
            tails += 1
            if tails > 0:
                text += 'T'
                time.sleep(.1)
                search = text.find(hth)
                #print flip, text, search  # testing
                
        print flip, text, search  # for testing only
        flips += 1
        if search != -1:
            print "needed", flips ," flips to get hth."
            flips = N

    print "you got", heads ," heads and", tails ," tails."
    rec = open('cointoss.txt', 'w')
    rec.write(text)
    rec.close()


# used to test module coinflip as a standalone program
# you can leave these lines in the module
if __name__ == '__main__':
    coinflip()

[lorayyne]

Your program does not work since you are trying to write to and read from the file at the same time. Store your temporary results in a string and then write to the file at the end ...

import random
import time

def coinflip():
    """flip the coin until you get an HTH pattern"""
    heads = 0
    tails = 0
    flips = 0
    hth = "HTH"

    # might be easier to set N to something like 50
    N = int(raw_input('Welcome to the Coin Toss!  '\
        'How many times do you want to flip the coin?: '))
    # optional, make sure N is large enough
    if N < 20:
        N = 20

    # create an empty string
    text = ""
    while (flips < N):
        flip = random.randint(1, 2)
        if flip == 1:
            heads += 1
            if heads > 0:
                text += 'H'
                time.sleep(.1)
                search = text.find(hth)
                #print flip, text, search  # testing
        else:
            tails += 1
            if tails > 0:
                text += 'T'
                time.sleep(.1)
                search = text.find(hth)
                #print flip, text, search  # testing
                
        print flip, text, search  # for testing only
        flips += 1
        if search != -1:
            print "needed", flips ," flips to get hth."
            flips = N

    print "you got", heads ," heads and", tails ," tails."
    rec = open('cointoss.txt', 'w')
    rec.write(text)
    rec.close()


# used to test module coinflip as a standalone program
# you can leave these lines in the module
if __name__ == '__main__':
    coinflip()

Cool, I'll try that! I thought that would pose a problem somewhere. Thanks!