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Basic coin flipper program - logical error help

P: n/a
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

Feb 22 '06 #1
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12 Replies


P: n/a
On Tue, 2006-02-21 at 16:14 -0800, DannyB wrote:
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?


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."
--
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.

Feb 22 '06 #2

P: n/a
DannyB wrote:
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):
coin = random.randrange(2)

Claudio
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

Feb 22 '06 #3

P: n/a
DannyB wrote:
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

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
Feb 22 '06 #4

P: n/a
DannyB wrote:
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


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
Feb 22 '06 #5

P: n/a
DannyB wrote:
I'm just learning Python.
So am I :-)
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)
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).


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


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
Feb 22 '06 #6

P: n/a
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 =)

Feb 22 '06 #7

P: n/a
wes weston wrote:
Looping is easier with:
for x in range(100):
if random.randint(0,1) == 0:
heads += 1
else:
tails += 1


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."
Feb 22 '06 #8

P: n/a

John Zenger wrote:
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))


Or a filter/map/lambda free way:

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

Feb 22 '06 #9

P: n/a
<bo****@gmail.com> wrote in message
news:11**********************@g43g2000cwa.googlegr oups.com...

John Zenger wrote:
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))


Or a filter/map/lambda free way:

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

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

Feb 22 '06 #10

P: n/a
wes weston wrote:
DannyB wrote:
I'm just learning Python. I've created a simple coin flipper program -

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


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)
Feb 22 '06 #11

P: n/a
DannyB said unto the world upon 21/02/06 06:14 PM:
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)
<snip>

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


<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
Feb 22 '06 #12

P: n/a

"Paul McGuire" <pt***@austin.rr._bogus_.com> wrote in message
news:yU******************@tornado.texas.rr.com...
<bo****@gmail.com> wrote in message
news:11**********************@g43g2000cwa.googlegr oups.com... 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

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 - ***

Feb 22 '06 #13

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