Re: Probability Problem
I think I got it. I noticed my code is essentially the same as Tim Peter's (plus the part of the problem he skipped). I read his code 20 minutes before recreating mine from Alex's hints. Thanks! def main(): ways = ways_to_roll() total_ways = float(101**10) running_total = 0 for i in range(1000-390+1): j = i + 390 running_total += ways[i] * ways[j] print running_total / total_ways**2 print ways[:10] def ways_to_roll(): result = [1] for i in xrange(10): result = combine([1] * 101, result) return result def combine(a, b): results = [0] * (len(a) + len(b) - 1) for i, ele in enumerate(a): for j, ele2 in enumerate(b): results[i+j] += ele * ele2 return results main() # output: 3.21962542309e-05 and # [1, 10, 55, 220, 715, 2002, 5005, 11440, 24310, 48620] # 3.21962542309e-05 is 32 out of a million On Apr 24, 2006, at 9:14 PM, Alex Martelli wrote: Elliot Temple [EMAIL PROTECTED] wrote: On Apr 24, 2006, at 8:24 PM, Alex Martelli wrote: Lawrence D'Oliveiro [EMAIL PROTECTED] wrote: In article [EMAIL PROTECTED], Elliot Temple [EMAIL PROTECTED] wrote: Problem: Randomly generate 10 integers from 0-100 inclusive, and sum them. Do that twice. What is the probability the two sums are 390 apart? I think the sum would come close to a normal distribution. Yes, very close indeed, by the law of large numbers. However, very close (in a math course at least) doesn't get the cigar. You can compute the requested answer exactly with no random number generation whatsoever: compute the probability of each result from 0 to 1000, then sum the probabilities of entries that are exactly 390 apart. That was the plan, but how do I get the probability of any given result? (in a reasonable amount of time) BTW I'm not in a math course, just curious. OK, I'll trust that last assertion (sorry for the hesitation, but it's all too easy to ``help'' somebody with a homework assignment and actually end up damaging them by doing it FOR them!-). I'm still going to present this in a way that stimulates thought, rather than a solved problem -- humor me...!-) You're generating a uniformly distributed random number in 0..100 (101 possibilities), 10 times, and summing the 10 results. How do you get a result of 0? Only 1 way: 0 at each attempt -- probability 1 (out of 1010 possibilities). How do you get a result of 1? 10 ways: 1 at one attempt and 0 at each of the others - probability 10 (again in 1010'ths;-). How do you get a result of 2? 10 ways for '2 at one attempt and 0 at each of the others', plus, 10*9/2 ways for '1 at two attempts and 0 at each of the others' -- probability 55 (ditto). ...and so forth, but you'd rather not work it out... So, suppose you start with a matrix of 101 x 10 entries, each of value 1 since all results are equiprobable (or, 1/1010.0 if you prefer;-). You want to compute the number in which you can combine two rows. How could you combine the first two rows (each of 101 1's) to make a row of 201 numbers corresponding to the probabilities of the sum of two throws? Suppose you combine the first entry of the first row with each entry of the second, then the second entry of the first row with each entry of the second, etc; each time, you get a sum (of two rolls) which gives you an index of a entry (in an accumulator row starting at all zeros) to increment by the product of the entries you're considering... Can you generalize that? Or, do you need more hints? Just ask! Alex -- http://mail.python.org/mailman/listinfo/python-list -- Elliot Temple http://www.curi.us/blog/ -- http://mail.python.org/mailman/listinfo/python-list
Probability Problem
Problem: Randomly generate 10 integers from 0-100 inclusive, and sum them. Do that twice. What is the probability the two sums are 390 apart? I have code to do part of it (below), and I know how to write code to do the rest. The part I have calculates the number of ways the dice can come out to a given number. The problem is the main loop has 9 iterations and it takes about 2.5 minutes to begin the 4th one, and each iteration is about 101 times longer than the previous one. So: x = 2.5 * 101**6 x /= (60*24*365.25) x 5045631.5622908585 It'd take 5,000 millennia. (If my computer didn't run out of memory after about 4 minutes, that is.) Any suggestions? Either a way to do the same thing much more efficiently (enough that I can run it) or a different way to solve the problem. Code: li = range(101) li2 = [] range101 = range(101) for x in xrange(9): print x is %s % x li2 = [] for y in li: for z in range101: li2 += [y+z] li = li2 print li.count(800) # prints how many ways the dice can add to 800 This link may help: http://www.math.csusb.edu/faculty/stanton/m262/intro_prob_models/ calcprob.html -- Elliot Temple http://www.curi.us/blog/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Probability Problem
On Apr 24, 2006, at 8:24 PM, Alex Martelli wrote: Lawrence D'Oliveiro [EMAIL PROTECTED] wrote: In article [EMAIL PROTECTED], Elliot Temple [EMAIL PROTECTED] wrote: Problem: Randomly generate 10 integers from 0-100 inclusive, and sum them. Do that twice. What is the probability the two sums are 390 apart? I think the sum would come close to a normal distribution. Yes, very close indeed, by the law of large numbers. However, very close (in a math course at least) doesn't get the cigar. You can compute the requested answer exactly with no random number generation whatsoever: compute the probability of each result from 0 to 1000, then sum the probabilities of entries that are exactly 390 apart. That was the plan, but how do I get the probability of any given result? (in a reasonable amount of time) BTW I'm not in a math course, just curious. -- Elliot Temple http://www.curi.us/blog/ -- http://mail.python.org/mailman/listinfo/python-list
Scope
I want to write a function, foo, so the following works: def main(): n = 4 foo(n) print n #it prints 7 if foo needs to take different arguments, that'd be alright. Is this possible? I already tried this (below), which doesn't work. foo only changes the global n. n = 3 def main(): def foo(var, context, c2): exec var + = 7 in context, c2 n = 4 foo(n, locals(), globals()) print n if __name__ == '__main__': main() print n And of course I tried: def inc(n): ... n += 3 ... a = 4 inc(a) a 4 -- Elliot Temple http://www.curi.us/ --- [This E-mail scanned for viruses by Declude Virus] -- http://mail.python.org/mailman/listinfo/python-list
Re: Scope
On Jun 4, 2005, at 2:13 AM, Leif K-Brooks wrote: Elliot Temple wrote: I want to write a function, foo, so the following works: def main(): n = 4 foo(n) print n #it prints 7 What's wrong with: def foo(n): return 7 def main(): n = 4 n = foo(n) print n Anything else (including the tricks involving mutable objects that will no doubt be posted) will result in ugly, hard to maintain code. Nothing is wrong with it in this case. I just want to know if Python can do what I said. -- Elliot Temple http://www.curi.us/ --- [This E-mail scanned for viruses by Declude Virus] -- http://mail.python.org/mailman/listinfo/python-list
Re: Moving Places, Subtracting from slices/lists
On Jun 2, 2005, at 12:12 AM, Mark Sargent wrote: Hi All, getting closer, me thinks. hotcat = ['Cat', 'roof', 'on', 'a', 'hot', 'tin'] for x in hotcat[:]: ... if x == 'roof': hotcat.insert(6,x) ... del hotcat[x] ... Traceback (most recent call last): File stdin, line 3, in ? TypeError: list indices must be integers How do I get that x to be an integer b4 it is entered into the indice.? Cheers. if you add print x to the loop you will see that X is the various words. to get an integer, you could search the list for the index of x. but that's lame. btw hotcat[:] is a *copy* of hotcat, so just leave out [:] enumerate is a function that adds indexes to a list. observe: hotcat = ['Cat', 'roof', 'on', 'a', 'hot', 'tin'] for index, word in enumerate(hotcat): if word == 'roof': del hotcat[index] you could also use a list comprehension hotcat = ['Cat', 'roof', 'on', 'a', 'hot', 'tin'] hotcat = [x for x in hotcat if x != 'roof'] -- Elliot Temple http://www.curi.us/ --- [This E-mail scanned for viruses by Declude Virus] -- http://mail.python.org/mailman/listinfo/python-list
Re: (OT) lincense protection generator
Why not check if all files you use are in appropriate directories, but not worry about same computer? You could also use some kind of hash on all your files, and check that they haven't been changed using that (ie, do they still hash to the same value they are supposed to?). (I know very little about hashes, so don't ask me for details.) On Jun 2, 2005, at 9:33 PM, flupke wrote: I'm going to be distributing a program based on wxPython python in a few weeks time. The code will run on windows machines. Because i don't want the users to move the folders around or mess with the program or taking copies home to fiddle with it, i was thinking of a way to check when the program starts that it's still on the same directory and same computer. That way i at least avoid unnecessary phone calls asking me for help when they messed the program up. I'm thinking of a function that will generate such a code and put it in a file. Then when the program starts it checks this file and checks the code in there with a code that it generates at that time again based for instance on the current directory and other components unique to that computer. It could be a long string (but what info?) and then take a hash from it and store the hash value. How could i construct such a code without being a total pain? For instance i don't want to check for anything hardware related because then my program would fail to work once the people change their hardware. Anyway, it doesn't need to be waterproof. (not possible anyway) Any ideas? Regards, Benedict -- http://mail.python.org/mailman/listinfo/python-list -- Elliot Temple http://www.curi.us/ --- [This E-mail scanned for viruses by Declude Virus] -- http://mail.python.org/mailman/listinfo/python-list
Pressing A Webpage Button
How do I make Python press a button on a webpage? I looked at urllib, but I only see how to open a URL with that. I searched google but no luck. For example, google has a button input type=submit value=Google Search name=btnG how would i make a script to press that button? Just for fun, is there any way to do the equivalent of typing into a text field like the google search field before hitting the button? (I don't actually need to do this.) If someone could point me in the right direction it'd be appreciated. -- Elliot Temple http://www.curi.us/ --- [This E-mail scanned for viruses by Declude Virus] -- http://mail.python.org/mailman/listinfo/python-list
Re: Beginner question: Logs?
On Jun 1, 2005, at 9:04 PM, Svens wrote: Hey thanks... Still getting an error message though. Here's what i'm doing: -- import math log10(15625) -- -It says that log10 is not defined, but it is since the module is imported, right? do either import math math.log10(15625) from math import * log10(15625) from math import log10 log10(15625) -- Elliot Temple http://www.curi.us/ --- [This E-mail scanned for viruses by Declude Virus] -- http://mail.python.org/mailman/listinfo/python-list
Re: need help of RE
On May 29, 2005, at 12:39 AM, cheng wrote: hi all a string like (word1 (Word2|woRd3)) how can i use the re to split it to ['word1', 'word2', 'word3'] Could you be more exact about what the string is like? Does it literally contain the characters '' and '|' ? If so, just split at them. -- Elliot Temple http://www.curi.us/ --- [This E-mail scanned for viruses by Declude Virus] -- http://mail.python.org/mailman/listinfo/python-list
Re: need help of RE
On May 29, 2005, at 12:57 AM, cheng wrote: im sorry, my engilsh is not vell well, the string not only contain '' and '|' and it can be anyting i just want to split out the whole word inside the string If the string could be anything, how do you know where the words are? If it's whitespace that separates words, try out str.split() -- Elliot Temple http://www.curi.us/ --- [This E-mail scanned for viruses by Declude Virus] -- http://mail.python.org/mailman/listinfo/python-list
Re: Case Sensitive, Multiline Comments
On May 29, 2005, at 11:44 AM, Arthur wrote: On 26 May 2005 17:33:33 -0700, Elliot Temple [EMAIL PROTECTED] wrote: Thanks for the link on case sensitivity. I'm curious about the person who found case sensitivity useful though: what is it useful for? I am curious about why you find case sensitivity annoying. But just mildly curious. I'm glad you asked ;-) Case insensitivity gives you more choice about how to type keywords that you have no control over. if or If. for or For. i don't think being inconsistent within a single program is a good idea, but having your choice of which to do is nice. I personally think all lowercase is good, but some languages have capitalised keywords, so apparently other people prefer that. I don't think the case sensitivity hurts beginners argument is persuasive. Anyone who seriously wants to program can look up the correct capitalisation of everything. *If* having to look up or keep track of capitalisation is annoying, *then* that argument applies to experienced programmers (who are devoting memory to the issue) just as much as beginners. -- Elliot Temple http://www.curi.us/ --- [This E-mail scanned for viruses by Declude Virus] -- http://mail.python.org/mailman/listinfo/python-list
Re: String manipulations
On May 28, 2005, at 2:52 PM, Lorn wrote:
Yes, that would get rid of the decimals... but it wouldn't get rid of
the extraneous precision. Unfortunately, the precision out to the ten
thousandth is noise... I don't need to round it either as the numbers
are artifacts of an integer to float conversion. Basically, I need to
know how many decimal places there are and then make the necessary
deletions before I can normalize by adding zeros, multiplying, etc.
Thanks for your suggestion, though.
for s in numbers:
decimal_index = s.find('.')
decimal_places = len(s) - decimal_index - 1
Anything wrong with this? (it will mess up if there isn't a decimal
but you can fix that if you want)
-- Elliot Temple
http://www.curi.us/
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Re: Case Sensitive, Multiline Comments
One other interesting thing about case sensitivity I don't think anyone has mentioned: in Python keywords are all lowercase already (the way I want to type them). In some other languages, they aren't... -- Elliot Temple http://www.curi.us/ --- [This E-mail scanned for viruses by Declude Virus] -- http://mail.python.org/mailman/listinfo/python-list
Re: Get number of lines in file
On May 27, 2005, at 12:17 PM, [EMAIL PROTECTED] wrote:
I have read in a file and need to get the number of lines.
cpn_file = open('Central Part number list.txt')
cpn_version = cpn_file.read().split('\n')
I want to know the number of elements in cpn_version.
Could you use:
count_lines = len(cpn_file.readlines())
-- Elliot Temple
http://www.curi.us/
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Case Sensitive, Multiline Comments
Hi I have two questions. Could someone explain to me why Python is case sensitive? I find that annoying. Also, why aren't there multiline comments? Would adding them cause a problem of some sort? Thanks, Elliot -- http://mail.python.org/mailman/listinfo/python-list
Re: Strange Execution Times
hey FYI i found the problem: i accidentally copied an output file for my test data. so all the passwords were exactly 32 chars long. so when replacing them with new 32 char passwords, it went much much faster, I guess because the list kept the same number of chars in it and didn't have to copy lots of data around. -- http://mail.python.org/mailman/listinfo/python-list
