Computer Programming 150

(April 10, 2008)

Lab 13a.py – Coin Tossing Simulation

#

# Name:

# File: Lab13a.py

# Date: April 10, 2008

#

# Desc : Simple Coin Tossing Simulation

#

from random import randrange

from myGraphics import drawList

class Coin:

def __init__(self):

" state of coin is either character H or T"

self.HTList = ["T", "H"]

self.value = self.HTList[randrange(0,2)]

def toss(self):

" toss coin"

self.value = self.HTList[randrange(0,2)]

def getValue(self):

" return state - either H or T "

return self.value

def __str__(self):

" implicit call returns state as string"

if self.value == "T":

return "Tails"

else:

return "Heads"

def main():

# display title

print "Coin Toss Program"

# get number of coins to toss per trial

numTosses = input("\nEnter number of times to toss a coin: ")

# ask before iterating loop

again = "y"

while (again == "y"):

# get number of trials to run

n = input("\nEnter number of Trials to run: ")

print

# initialize count array to all zeros

headCount = [0]*(numTosses+1)

# create a coin object

c = Coin()

for i in range(n):

# execute one trial - count number of heads

cnt = 0

for j in range(numTosses):

c.toss()

if c.getValue() == "H":

cnt = cnt + 1

# increment count for that number of heads

headCount[cnt] = headCount[cnt] + 1

# display table of results

print "Heads | Count"

for i in range(numTosses+1):

print " %2d %4d" % (i, headCount[i])

# graph distribution

drawList(headCount, "Frequency Distribution")

# ask to go again

again = raw_input("\nAgain? (y/n): ")

main()

Lab13b.py – DNA Codon String Search

#

# Name:

# File: Lab13b.py

# Date: April 10, 2008

#

# Desc: DNA Codon Search

#

from random import randrange

def randString(n):

#

# returns a random string of G's A', T's and C's

#

str = ""

charList = ["G", "A", "T", "C"]

for i in range(n):

str = str + charList[randrange(0,4)]

return str

def main():

# display title

print "DNA Codon Search"

# ask before iterating loop

again = "y"

while (again == "y"):

# generate a random string of length n

n = input("\nEnter Length of String: ")

str1 = randString(n)

print str1

print

# get search string (a.k.a. codon)

str2 = raw_input("Enter search string: ")

n = len(str2)

indexList = []

# search for all occurrences of str2 in str1

for i in range(len(str1)):

if str2 == str1[i:i+n]:

indexList.append(i)

# display results

if len(indexList) == 0:

print str2, "not found"

else:

print str2, "found at", indexList

# go again?

again = raw_input("\nAgain? (y/n): ")

main()