Basic coin flipper program - logical error help

I'm just learning Python. I've created a simple coin flipper program -
here is the code:

[source]
#Coin flipper
import random

heads = 0
tails = 0
counter = 0

coin = random.randrange(2)

while (counter < 100):
if (coin == 0):
heads += 1
counter += 1
else:
tails += 1
counter += 1

coin = random.randrange(2)

print "\nThe coin landed on heads", heads, "times."
print "\nThe coin landed on tails", tails, "times."
[/source]

<<<I'm sure the [source] tags don't work - I through them in there
anyway.>>>

The program runs - however - it will give me 100 heads OR 100 tails.
Can someone spot the logic error?

Thanks

~Dan

On Tue, 2006-02-21 at 16:14 -0800, DannyB wrote:[color=blue]
> I'm just learning Python. I've created a simple coin flipper program -
> here is the code:
>
> [source]
> #Coin flipper
> import random
>
> heads = 0
> tails = 0
> counter = 0
>
> coin = random.randrange(2)
>
> while (counter < 100):
> if (coin == 0):
> heads += 1
> counter += 1
> else:
> tails += 1
> counter += 1
>
> coin = random.randrange(2)
>
>
> print "\nThe coin landed on heads", heads, "times."
> print "\nThe coin landed on tails", tails, "times."
> [/source]
>
> <<<I'm sure the [source] tags don't work - I through them in there
> anyway.>>>
>
> The program runs - however - it will give me 100 heads OR 100 tails.
> Can someone spot the logic error?[/color]

Yes. Put coin = random.randrange(2) inside the while loop.

import random

heads = 0
tails = 0
counter = 0

coin = random.randrange(2)

while (counter < 100):
if (coin == 0):
heads += 1
counter += 1
else:
tails += 1
counter += 1

coin = random.randrange(2)

print "\nThe coin landed on heads", heads, "times."
print "\nThe coin landed on tails", tails, "times."

--
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DannyB wrote:[color=blue]
> I'm just learning Python. I've created a simple coin flipper program -
> here is the code:
>
> [source]
> #Coin flipper
> import random
>
> heads = 0
> tails = 0
> counter = 0
>
> while (counter < 100):[/color]

coin = random.randrange(2)

Claudio
[color=blue]
> if (coin == 0):
> heads += 1
> counter += 1
> else:
> tails += 1
> counter += 1
>
> coin = random.randrange(2)
>
>
> print "\nThe coin landed on heads", heads, "times."
> print "\nThe coin landed on tails", tails, "times."
> [/source]
>
> <<<I'm sure the [source] tags don't work - I through them in there
> anyway.>>>
>
> The program runs - however - it will give me 100 heads OR 100 tails.
> Can someone spot the logic error?
>
> Thanks
>
> ~Dan
>[/color]

DannyB wrote:[color=blue]
> I'm just learning Python. I've created a simple coin flipper program -
> here is the code:
>
> [source]
> #Coin flipper
> import random
>
> heads = 0
> tails = 0
> counter = 0
>
> coin = random.randrange(2)
>
> while (counter < 100):
> if (coin == 0):
> heads += 1
> counter += 1
> else:
> tails += 1
> counter += 1
>
> coin = random.randrange(2)
>
>
> print "\nThe coin landed on heads", heads, "times."
> print "\nThe coin landed on tails", tails, "times."
> [/source]
>
> <<<I'm sure the [source] tags don't work - I through them in there
> anyway.>>>
>
> The program runs - however - it will give me 100 heads OR 100 tails.
> Can someone spot the logic error?
>
> Thanks
>
> ~Dan
>[/color]
Looks an awful lot like your homework, but I'll give you a clue.
You need to get the your coin tosses inside your loop. Otherwise
you only toss the coin once and then loop 100 times with the
same value.

-Larry Bates

DannyB wrote:[color=blue]
> I'm just learning Python. I've created a simple coin flipper program -
> here is the code:
>
> [source]
> #Coin flipper
> import random
>
> heads = 0
> tails = 0
> counter = 0
>
> coin = random.randrange(2)
>
> while (counter < 100):
> if (coin == 0):
> heads += 1
> counter += 1
> else:
> tails += 1
> counter += 1
>
> coin = random.randrange(2)
>
>
> print "\nThe coin landed on heads", heads, "times."
> print "\nThe coin landed on tails", tails, "times."
> [/source]
>
> <<<I'm sure the [source] tags don't work - I through them in there
> anyway.>>>
>
> The program runs - however - it will give me 100 heads OR 100 tails.
> Can someone spot the logic error?
>
> Thanks
>
> ~Dan
>[/color]

Dan,
Looping is easier with:
for x in range(100):
if random.randint(0,1) == 0:
heads += 1
else:
tails += 1

Inside the loop you need to "flip" on each pass.
You're "flipping" once before the start of the loop now.
wes

DannyB wrote:[color=blue]
> I'm just learning Python.[/color]

So am I :-)
[color=blue]
> I've created a simple coin flipper program -
> here is the code:
>
> [source]
> #Coin flipper
> import random
>
> heads = 0
> tails = 0
> counter = 0
>
> coin = random.randrange(2)
>
> while (counter < 100):
> if (coin == 0):
> heads += 1
> counter += 1
> else:
> tails += 1
> counter += 1
>
> coin = random.randrange(2)[/color]

This line is you logic error because it's not part of your while loop
the coin variables get the result of random.randrange(2) assigned only
one time (before the loop).
[color=blue]
>
>
> print "\nThe coin landed on heads", heads, "times."
> print "\nThe coin landed on tails", tails, "times."
> [/source]
>
> <<<I'm sure the [source] tags don't work - I through them in there
> anyway.>>>
>
> The program runs - however - it will give me 100 heads OR 100 tails.
> Can someone spot the logic error?
>
> Thanks
>
> ~Dan
>[/color]

You could changed the program to this it works too and is just as
readable (IMHO):

#Coin flipper
import random

heads = 0
tails = 0
counter = 0
# removed random line
while (counter < 100):
if random.randrange(2): # put random here
heads += 1
counter += 1
else:
tails += 1
counter += 1
# removed random line
print "\nThe coin landed on heads", heads, "times."
print "\nThe coin landed on tails", tails, "times."

Take my advice with caution I'm also new to this :-)

Btw, it is possible that the coins lands on it side if not catched with
the hand (yes I have seen it happen) ;-)

--
mph

Thanks everyone for your insight.

I'm coming from C++ - I'm used to formatting code with {} instead of
whitespaces.

@Larry - this isn't my homework :P I'm actually taking a VB.NET class
in school.

I was teaching myself C++ but decided to scale back to Python. I've
heard it was a bit easier to understand and it cuts your development
time by at least 50% (I've heard 90%).

Logically I can figure things out - its the formatting of the logic in
Python that is messing me up. I'll get it soon enough =)

wes weston wrote:[color=blue]
> Looping is easier with:
> for x in range(100):
> if random.randint(0,1) == 0:
> heads += 1
> else:
> tails += 1[/color]

Also, with the functional programming tools of map, filter, and lambda,
this code can be reduced to just six lines:

import random

flips = map(lambda x: random.randrange(2), xrange(100))
heads = len(filter(lambda x: x is 0, flips))
tails = len(filter(lambda x: x is not 0, flips))

print "The coin landed on heads", heads, "times."
print "The coin landed on tails", tails, "times."

John Zenger wrote:[color=blue]
> Also, with the functional programming tools of map, filter, and lambda,
> this code can be reduced to just six lines:
>
> import random
>
> flips = map(lambda x: random.randrange(2), xrange(100))
> heads = len(filter(lambda x: x is 0, flips))
> tails = len(filter(lambda x: x is not 0, flips))[/color]

Or a filter/map/lambda free way:

heads = sum(random.randrange(2) for x in xrange(100))
tails = 100 - heads

<bonono@gmail.com> wrote in message
news:1140578858.586591.243900@g43g2000cwa.googlegr oups.com...[color=blue]
>
> John Zenger wrote:[color=green]
> > Also, with the functional programming tools of map, filter, and lambda,
> > this code can be reduced to just six lines:
> >
> > import random
> >
> > flips = map(lambda x: random.randrange(2), xrange(100))
> > heads = len(filter(lambda x: x is 0, flips))
> > tails = len(filter(lambda x: x is not 0, flips))[/color]
>
> Or a filter/map/lambda free way:
>
> heads = sum(random.randrange(2) for x in xrange(100))
> tails = 100 - heads
>[/color]
sort, then groupby.

import itertools
import random
h,t = [len(list(g)) for k,g in itertools.groupby(sorted([random.randrange(2)
for i in xrange(100)]))]
print h,t

wes weston wrote:[color=blue]
> DannyB wrote:
>[color=green]
>> I'm just learning Python. I've created a simple coin flipper program -[/color][/color]

....
[color=blue]
> Dan,
> Looping is easier with:
> for x in range(100):
> if random.randint(0,1) == 0:
> heads += 1
> else:
> tails += 1
>[/color]

Or, continuing with that theme:

for x in range(N):
heads += random.randint(0, 1)

As in:

import random
N = 100
heads = 0
for x in range(N):
heads += random.randint(0, 1)
print "%d heads and %d tails." % (heads, N - heads)

DannyB said unto the world upon 21/02/06 06:14 PM:[color=blue]
> I'm just learning Python. I've created a simple coin flipper program -
> here is the code:
>
> [source]
> #Coin flipper
> import random
>
> heads = 0
> tails = 0
> counter = 0
>
> coin = random.randrange(2)
>
> while (counter < 100):
> if (coin == 0):
> heads += 1
> counter += 1
> else:
> tails += 1
> counter += 1
>
> coin = random.randrange(2)[/color]

<snip>

[color=blue]
> The program runs - however - it will give me 100 heads OR 100 tails.
> Can someone spot the logic error?[/color]

<snip>

Your original question is long since answered. But I've a style point.
As Dennis Lee Bieber pointed out, you don't need all three
accumulators. If you keep to the overall style of your code, you can
avoid repeating yourself as:

while (counter < 100):
counter += 1 # No point in putting this in each branch
coin = random.randrange(2)
if (coin == 0):
heads += 1
else:
tails += 1

For roughly the same style, I'd go with:

heads = 0
count = 100

for i in range(count):
if random.randrange(2):
heads += 1

tails = count - heads

HTH,

Brian vdB

"Paul McGuire" <ptmcg@austin.rr._bogus_.com> wrote in message
news:yURKf.22750$UN2.3873@tornado.texas.rr.com...[color=blue]
> <bonono@gmail.com> wrote in message
> news:1140578858.586591.243900@g43g2000cwa.googlegr oups.com...[/color]
[color=blue]
> sort, then groupby.
>
>
> import itertools
> import random
> h,t = [len(list(g)) for k,g in[/color]
itertools.groupby(sorted([random.randrange(2)[color=blue]
> for i in xrange(100)]))]
> print h,t
>
>[/color]
By the way, sort + groupby generalizes beyond just coin-flipping. Here is a
modified version that simulates die rolls.

-- Paul

import itertools
import random

NUM_ROLLS = 1000
dieRolls = [random.randrange(6)+random.randrange(6)+2 for i in
xrange(NUM_ROLLS)]

# create dummy list entries for impossible rolls of 0 and 1
rolls = [None,None]

rolls += [len(list(g)) for k,g in itertools.groupby(sorted(dieRolls))]

# print out nice histogram
for i,r in enumerate(rolls):
if i > 1:
print "%2d - %s" % (i,"*"*int(round(r/10.0)))

prints:

2 - ***
3 - *****
4 - *********
5 - **********
6 - ***************
7 - ******************
8 - **************
9 - *********
10 - *******
11 - *******
12 - ***