from decimal import Decimal, getcontext
from random import randint
# Return 3 decimal places
getcontext().prec = 3
# Function "get_input" verifies the input. As "raw_input" does not accept an int
# as input (which is what we need), the function converts the input into a str
# and checks whether the str is a digit. If so it converts the str to an int and
# returns it. If not the user is prompted again for an input. A float is not a
# valid input ("isdigit" would not be True). You can convert an int to a str but
# not a float to a str. The return value is used to define the number of trials.
def get_input(prompt):
''' (str) --> int
Ask the user for input, convert it into a str, check for a digit and convert
into an int. Prompt as long as the user provides a valid input.
'''
trials = raw_input(prompt)
trials = str(trials)
while not trials.isdigit():
print "You have to provide an integer for the number of flips!"
trials = raw_input(prompt)
return int(trials)
heads = 0
tail = 0
i = 0
print "\n"
flip = get_input("How often shall I flip a coin? ")
print "\nFlipping the coin ..."
while i < int(flip):
coin = randint(1,2)
if coin == 1:
heads += 1
else:
tail += 1
i += 1
relfreq_heads = Decimal(heads) / Decimal(int(flip))
relfreq_tail = Decimal(tail) / Decimal(int(flip))
print "\nFlipping a coin", flip, "times yields:\n"
print "Outcome\t\tFrequency\tRelative Frequency"
print "=======\t\t=========\t=================="
print "Heads\t\t", heads, "\t\t", relfreq_heads
print "Tail\t\t", tail, "\t\t", relfreq_tail
