Re: [Tutor] Limit raw_input to hundredth decimal point
Thanks all! This helps a lot.
On Jul 1, 2011, at 6:13 AM, Steven D'Aprano wrote:
> Ryan Kirk wrote:
>> Is there a way to limit raw_input to the hundredth decimal point?
>
> No. raw_input is a tool that does one thing: it collects input from the user.
> It doesn't understand numbers, check for decimal places, check the input for
> spelling errors, or anything else. It's a hammer, not a combination
> hammer-screwdriver-wrench-drill-saw-axe :)
>
> One solution is to build a new tool that checks for decimal places:
>
>
> def check(text):
>try:
>x = float(text)
>except ValueError:
>print "please enter a number"
>return None
>y = x*100
>if y - int(y) != 0:
>print "please enter only two decimal places"
>return None
>return x
>
>
> def get_number(prompt):
>answer = None
>while answer is None:
>text = raw_input(prompt)
>answer = check(text)
>return answer
>
>
> At first, this seems to work well:
>
> >>> get_number("Please enter a number with two decimal places: ")
> Please enter a number with two decimal places: 77.25
> 77.25
> >>>
>
> but there's a fundamental problem. The user is entering numbers in decimal
> (base 10), but Python does calculations in binary (base 2), and something
> that has two decimal places may not be exact in binary:
>
> >>> get_number("Please enter a number with two decimal places: ")
> Please enter a number with two decimal places: 77.21
> please enter only two decimal places
>
> Huh? 77.21 does have two decimal places. But the closest float to 77.21 is in
> fact 77.204. No computer on Earth can store 77.21 *exactly* as a
> binary float, no matter how hard you try!
>
> So, what to do...? You can:
>
> (1) Give up on forcing the user to only enter two decimal places, and instead
> use the round() function to round to two places:
>
> >>> round(77.2123456, 2)
> 77.204
>
> This is still not two decimal places, but it is the closest possible float to
> 7.21, so you can't do any better.
>
> (2) Or give up on using float, and use the decimal module instead. (However
> decimals are slower and less convenient than floats.)
>
> >>> from decimal import Decimal
> >>> x = Decimal("77.21")
> >>> x
> Decimal("77.21")
>
>
> If you are working with currency, then you should use decimal, and not floats.
>
>
>
> Good luck!
>
>
>
> --
> Steven
>
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Re: [Tutor] (no subject)
On Fri, Jul 1, 2011 at 7:11 PM, David Merrick wrote:
> NameError: global name 'stash' is not defined
>
>
There are a _lot_ of missing pieces here; I think you started writing code
without a plan of how your game would actually run. The current error is
only the first you're going to run into here... That being said, we might
as well fix the first one.
You either have several problems here, or just one; I'm going to go for the
"just one" option: I'm going to assume that you actually want "stash" to be
an attribute of a Bet object - I think that it should be an attribute of
each player, not of their individual bets, but that's another issue.
The only time you can refer to a variable without qualifying it is from
within the same block of code. Otherwise, the interpreter has to guess
which context (also known as "scope") the variable is supposed to belong to,
and the interpreter refuses to guess. The error you're getting boils down
to "You referred to a variable called 'stash', but since you didn't define
it in the local scope, I assume it's a global variable - but you didn't
define it there either! What gives?"
In Bet.__init__(), you have
> stash = money
>
This makes "stash" a local variable in the scope of __init__(), and as soon
as __init__() terminates, so does "stash".
What you want is:
> self.stash = money
>
This makes "stash" an attribute of Bet.
To refer to "stash" from inside the Bet object, you need to refer to it as
"self.stash"; from outside, after you've created a Bet object ("bet =
Bet()") you need to refer to it as "bet.stash".
One more thing: you define Bet.__init__() as taking two parameters, "bet"
and "money"; you make "money" optional by defaulting it to 10, but "bet" has
no default, so if your program ever got around to executing "bet = Bet()" it
would blow up because of a missing parameter.
Also, your use of variable names is confusing. "bet = Bet()" is OK, but
ALSO having "bet" as a parameter to Bet.__init__()? Python won't be
confused, but I bet you will be - I know I am.
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[Tutor] Blackjack 2 - was Re: (no subject)
Please provide a meaningful subject!
"David Merrick" wrote ># Blackjack
class BJ_Game(object):
""" A Blackjack Game. """
def __init__(self, names):
self.players = []
for name in names:
player = BJ_Player(name)
self.players.append(player)
self.dealer = BJ_Dealer("Dealer")
self.deck = BJ_Deck()
self.deck.populate()
self.deck.shuffle()
bet = 0
bet = Bet()
bet.betting(stash)
def main():
print("\t\tWelcome to Blackjack!\n")
stash = 0
names = []
number = games.ask_number("How many players? (1 - 7): ", low = 1,
high > .
game = BJ_Game(names)
File "I:/Python/programs/blackjackBetting.py", line 224, in
main()
File "I:/Python/programs/blackjackBetting.py", line 216, in main
game = BJ_Game(names)
File "I:/Python/programs/blackjackBetting.py", line 147, in
__init__
bet.betting(stash)
NameError: global name 'stash' is not defined
It says stash is not defined. That means there is no
variable named stash visible to Python inside the
init method of BJ_Game.
The only stash defined is in the main function.
variables defined inside a function (including main()
are *only* visible within that function, nowhere else.
But you have lots of missing names all over.
I suggest you review yuour code before trying
to run it, otherwise you will be seeing a lot of
these error messages.
You will fund information about naming and scope
in the "Whats in a name?" topic of my tutorial.
HTH,
--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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[Tutor] Cython question
Hi, Some time ago I finished a sav reader for Spss .sav data files (also with the help of some of you!): http://code.activestate.com/recipes/577650-python-reader-for-spss-sav-files/ It works fine, but it is not fast with big files. I am thinking of implementing two of the functions in cython (getValueChar and getValueNum). As far as I understood it requires the functions to be re-written in a Python-like langauge, 'minus the memory manager'. That little piece of code is converted to C and subsequently compiled to a .dll or .so file. The original program listens and talks to that .dll file. A couple of questions: -is this a correct representation of things? -will the speed improvement be worthwhile? (pros) -are there reasons not to try this? (cons) -is it 'sane' to mix ctypes and cython for nonintensive and intensive operations, respectively? Thanks in advance! Cheers!! Albert-Jan ~~ All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us? ~~ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Cython question
Albert-Jan Roskam, 02.07.2011 11:49: Some time ago I finished a sav reader for Spss .sav data files (also with the help of some of you!): http://code.activestate.com/recipes/577650-python-reader-for-spss-sav-files/ It works fine, but it is not fast with big files. I am thinking of implementing two of the functions in cython (getValueChar and getValueNum). As far as I understood it requires the functions to be re-written in a Python-like langauge "rewritten" only in the sense that you may want to apply optimisations or provide type hints. Cython is Python, but with language extensions that allow the compiler to apply static optimisations to your code. , 'minus the memory manager'. Erm, not sure what you mean here. Cython uses the same memory management as CPython. That little piece of code is converted to C and subsequently compiled to a .dll or .so file. The original program listens and talks to that .dll file. A couple of questions: -is this a correct representation of things? More or less. Instead of "listens and talks", I'd rather say "uses". What you get is just another Python extension module which you can use like any other Python module. -will the speed improvement be worthwhile? (pros) Depends. If your code is I/O bound, then likely not. If the above two functions are true CPU bottlenecks that do some kind of calculation or data transformation, it's likely going to be faster in Cython. -are there reasons not to try this? (cons) If your performance problem is not CPU related, it may not be worth it. -is it 'sane' to mix ctypes and cython for nonintensive and intensive operations, respectively? Why would you want to use ctypes if you can use Cython? Stefan ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Cython question
"Albert-Jan Roskam" wrote As far as I understood it requires the functions to be re-written in a Python-like langauge, 'minus the memory manager'. Thats what I understand too, but I've only read the web docs :-) converted to C and subsequently compiled to a .dll or .so file. The original program listens and talks to that .dll file. I believe it effectively becomes a module that you import like any other. -will the speed improvement be worthwhile? (pros) That depends on the structure of your code. Profile it first to prove that the functions you are optimising are in fact the places where the bulk of the time is spent. Then check that those functions aren't spending their time calling C functions already. If all you have is a loop calling a fubction that is already in C then cython is unlikely to give huge improvement. But if you have a lot of python code doing real processing then yes cython (or similar) should make a significant difference (ie up to say, 10 times faster) -are there reasons not to try this? (cons) If you optimise the wrong bits you might just waste your time and it will make future maintenance more difficult because you have two environments to support. Have you tried optimising the Python code first? -is it 'sane' to mix ctypes and cython for nonintensive and intensive operations, respectively? In the same app yes, in the same function I'd guess probably not. But I'll let others with more experience of using both comment. But bear in mind I've only read the cython docs, not actually used it... HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Blackjack problem
Hi David (and Vincent, as I think you may be interested in this as well), On 2 July 2011 03:11, David Merrick wrote: > # Blackjack > # From 1 to 7 players compete against a dealer > I came accross this book ( http://homepage.mac.com/s_lott/books/oodesign/build-python/html/index.html ) on the internet today, which I submit may be helpful in your journey of learning. It specifically covers building object oriented design type skills (as opposed to learning Python or programming as such) and also has as subject matter the game of Blackjack (amongst several others.) The author also has 2 other books, one specifically for learning the basics of Python the language and another for learning the basics of programming in general, which may also be helpful. Anyway, hope that helps, Walter ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Cython question
Hi Stefan, Alan, Matt, Thanks for your replies. I used cProfile to find the bottlenecks, the two Python functions getValueChar and getValueNum. These two Python functions simply call two equivalent C functions in a .dll (using ctypes). The problem is that these functions are called as many times as there are VALUES in a file (e.g. 1000 records * 100 columns = 10 function calls). So if I understand you correctly, this is not Cpu bound and, therefore, alas, Cython won't improve the excution time. Correct? That .dll contains many more functions, for example to extract certain header information (a list of all the spss variables, etc.). Getting this kind of information is only done once per spss file. So, to answer your question, Stefan, I'd like this part of the code to remain the same, ie. with ctypes. Nothing much to win anyway, with just one function call per data file. Cython might be useful when the program is converting spss date/times (seconds since gregorian epoch) to iso-date/times. If I understand it correctly, this is certainly cpu bound. Btw, Matt, I indeed used psyco already, although I never precisely quantified the improvement in speed. Cheers!! Albert-Jan ~~ All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us? ~~ --- On Sat, 7/2/11, Stefan Behnel wrote: From: Stefan Behnel Subject: Re: [Tutor] Cython question To: tutor@python.org Date: Saturday, July 2, 2011, 1:29 PM Albert-Jan Roskam, 02.07.2011 11:49: > Some time ago I finished a sav reader for Spss .sav data files (also with the > help of some of you!): > http://code.activestate.com/recipes/577650-python-reader-for-spss-sav-files/ > > It works fine, but it is not fast with big files. I am thinking of > implementing > two of the functions in cython (getValueChar and getValueNum). > As far as I understood it requires the functions to be re-written in a > Python-like langauge "rewritten" only in the sense that you may want to apply optimisations or provide type hints. Cython is Python, but with language extensions that allow the compiler to apply static optimisations to your code. > , 'minus the memory manager'. Erm, not sure what you mean here. Cython uses the same memory management as CPython. > That little piece of code is > converted to C and subsequently compiled to a .dll or .so file. The original > program listens and talks to that .dll file. A couple of questions: > -is this a correct representation of things? More or less. Instead of "listens and talks", I'd rather say "uses". What you get is just another Python extension module which you can use like any other Python module. > -will the speed improvement be worthwhile? (pros) Depends. If your code is I/O bound, then likely not. If the above two functions are true CPU bottlenecks that do some kind of calculation or data transformation, it's likely going to be faster in Cython. > -are there reasons not to try this? (cons) If your performance problem is not CPU related, it may not be worth it. > -is it 'sane' to mix ctypes and cython for nonintensive and intensive > operations, respectively? Why would you want to use ctypes if you can use Cython? Stefan ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] problem with reading dns query
I have got a very simple idea in mind that i want to try out. Say i have a
browser, chrome for instance, and i want to search for the ip of the domain
name, say `www.google.com`. I use windows 7 and i have set the dns lookup
properties to manual and have given the address `127.0.0.1` where my server
(written in Python) is running. I started my server and i could see the dns
query like this:
WAITING FOR CONNECTION.
.recieved from : ('127.0.0.1', 59339)
"'~\\x17\\x01\\x00\\x00\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x03www\\x06google\\x02co\\x02in\\x00\\x00\\x01\\x00\\x01'"
The `waiting for connection` and the `received from` is from my server. How
do i get a breakdown form(a human readable form) of this message??
This is my server code(quiet elementary but still):
Here is the code:
from time import sleep
import socket
host=''
port=53
addr_list=(host,port)
buf_siz=1024
udp=socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
udp.bind(addr_list)
while True:
print 'WAITING FOR CONNECTION.'
data,addr = udp.recvfrom(buf_siz) print '.recieved from :
',addr
sleep(3)
print repr(data)
is there any better way to get the dns request fro my browser first ,extract
the domain name and then send it to a name server that i wish all in python
? if here is pl explain it without any third party modules i wouldn mind
re-inventing the wheel as long as i can learn all python concepts properly
Thanking you in advance!!!
Yours thankfully,
Preetam
(A python freak)
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Re: [Tutor] Cython question
"Albert-Jan Roskam" wrote I used cProfile to find the bottlenecks, the two Python functions getValueChar and getValueNum. These two Python functions simply call two equivalent C functions in a .dll (using ctypes). In that case cythin will speed up the calling loops but it can't do anything to speed up the DLL calls, you have effectively already optimised those functions by calling the DLL. The problem is that these functions are called as many times as there are VALUES in a file It might be worth a try if you have very big data sets because a C loop is faster than a Python loop. But don't expect order of magnitude improvements. So if I understand you correctly, this is not Cpu bound and, therefore, alas, Cython won't improve the excution time. Correct? It may still be CPU bound in that the CPU is doing all the work, but if the CPU time is in the DLL functions rather than in the loop cython won't help much. CPU bound refers to the type of processing - is it lots of logic, math, control flows etc? Or is it I/O bound - reading network, disk, or user input? Or it might be memory bound - creating lots of in memory objects (especially if that results in paging to disk, when it becomes I/O bound too!) Knowing what is causing the bottleneck will determine how to improve things. Use tools like TaskManager in Windows or top in *nix to see where the time is going and what resources are being consumed. Fast code is not always the answer. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] problem with reading dns query
"preetam shivaram" wrote browser, chrome for instance, and i want to search for the ip of the domain name, say `www.google.com`. I'm curious why you would want to? Given the volatility of IP addresses in the modern network I'm not sure what good it would do you? (as opposed to doing it manually using standard networking tools like ping, traceroute etc) `127.0.0.1` where my server (written in Python) is running. localhost is not usually a good place to test networking tools. Even if you used a local LAN IP address allocated via DHCP it would be slightly more realistic. is there any better way to get the dns request fro my browser first ,extract the domain name and then send it to a name server that i wish all in python You could set your local DNS settings to your local server. But if you want to reroute DNS I suspect there are esierways. But I'm still not clear about what you really want to do here, or why? -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Cython question
Alan Gauld, 02.07.2011 15:28: "Albert-Jan Roskam" wrote I used cProfile to find the bottlenecks, the two Python functions getValueChar and getValueNum. These two Python functions simply call two equivalent C functions in a .dll (using ctypes). The code is currently declared as Windows-only and I don't know any good C-level profiling code for that platform. Under Linux, once I'm sure I have a CPU bound problem below the Python level, I'd use valgrind and KCacheGrind to analyse the performance. That will include all C function calls (and even CPU instructions, if you want) in the call trace. Makes it a bit less obvious to see what Python is doing, but leads to much more detailed results at the C level. It's also worth keeping in mind that all profiling attempts *always* interfere with the normal program execution. The results you get during a profiling run may not be what you'd get with profiling disabled. So, profiling is nice, but it doesn't replace proper benchmarking. In that case cythin will speed up the calling loops but it can't do anything to speed up the DLL calls, you have effectively already optimised those functions by calling the DLL. The problem is that these functions are called as many times as there are VALUES in a file It might be worth a try if you have very big data sets because a C loop is faster than a Python loop. But don't expect order of magnitude improvements. Looking at the code now, it's actually worse than that. The C function call does not only go through ctypes, but is additionally wrapped in a method call. So the OP is paying the call overhead twice for each field, plus the method lookup and some other operations. These things can add up quite easily. So, iff the conversion code is really a CPU bottleneck, and depending on how much work the C functions actually do, the current call overhead, 100 times per record, may be a substantial part of the game. It's worth seeing if it can be dropped at the Python level by removing method lookup and call levels (i.e. by inlining the method), but if that's not enough, Cython may still be worth it. For one, Cython's call overhead is lower than that of ctypes, and if the call is only done once, and the loop is moved into Cython (i.e. C) entirely, the overhead will also drop substantially. It might also be worth running the code in PyPy instead of CPython. PyPy will optimise a lot of the overhead away that this code contains. So if I understand you correctly, this is not Cpu bound I don't have enough information to comment on that. It may still be CPU bound in that the CPU is doing all the work, but if the CPU time is in the DLL functions rather than in the loop cython won't help much. CPU bound refers to the type of processing - is it lots of logic, math, control flows etc? Or is it I/O bound - reading network, disk, or user input? Or it might be memory bound - creating lots of in memory objects (especially if that results in paging to disk, when it becomes I/O bound too!) Knowing what is causing the bottleneck will determine how to improve things. Use tools like TaskManager in Windows or top in *nix to see where the time is going and what resources are being consumed. Fast code is not always the answer. That is very good advice. As a rule of thumb, a process monitor like top will tell you how much time is spent in I/O and CPU. If, during a test run (with profiling disabled, as that eats time, too!), your CPU usage stays close to 100%, your program is CPU bound. If, however, it stays lower, and the monitor reports a high I/O waiting time, it's I/O bound. In this case, I/O bound is what you want to achieve, because it means that your code is running faster than your hard drive can deliver the data. Stefan ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Algorithm for sequence matching
Hey I am looking for an algo for the largest sequence search in the two list. Example : list a accepts some say 'm' numbers. list b accept says 'n' numbers. I want to look for the largest same sequence between the two list and then display it. I tried out but failed to do so. Say A=[11,23,45,21,63,56,78,32] B=[56,78,11,23,45,21,111,234,56543] There are two similar sequence matching over here [11,23] and [23,45,21] i want to display second sequence because its larger in number. Plz help Thanks in Advance :) Ankur Aggarwal ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Algorithm for sequence matching
On 7/2/2011 4:30 PM, ANKUR AGGARWAL wrote: Hey I am looking for an algo for the largest sequence search in the two list. Example : list a accepts some say 'm' numbers. list b accept says 'n' numbers. I want to look for the largest same sequence between the two list and then display it. I tried out but failed to do so. Say A=[11,23,45,21,63,56,78,32] B=[56,78,11,23,45,21,111,234,56543] There are two similar sequence matching over here [11,23] and [23,45,21] i want to display second sequence because its larger in number. Makes no sense to me! Pleae explain so a dummy like me can understand. Also tell us what you tried and how it failed. -- Bob Gailer 919-636-4239 Chapel Hill NC ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Algorithm for sequence matching
Hi Ankur, On 2 July 2011 21:30, ANKUR AGGARWAL wrote: > Hey > I am looking for an algo for the largest sequence search in the two list. > > Example : list a accepts some say 'm' numbers. list b accept says 'n' > numbers. I want to look for the largest same sequence between the two list > and then display it. I tried out but failed to do so. > Say A=[11,23,45,21,63,56,78,32] > B=[56,78,11,23,45,21,111,234,56543] > > There are two similar sequence matching over here [11,23] and [23,45,21] i > want to display second sequence because its larger in number. Plz help > Thanks in Advance :) > Umm, what about [11,23,45,21]? That seems to be longer still so should be the best one to display, or? Walter ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Algorithm for sequence matching
Forwarding back to list. -- Forwarded message -- From: ANKUR AGGARWAL Date: 2 July 2011 22:23 Subject: Re: [Tutor] Algorithm for sequence matching To: Walter Prins ya sorry I forgot to include 11 . i want the answer to be [11,23,45,21] On Sun, Jul 3, 2011 at 2:46 AM, Walter Prins wrote: > Hi Ankur, > > Umm, what about [11,23,45,21]? That seems to be longer still so should be > the best one to display, or? > ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Algorithm for sequence matching
ANKUR AGGARWAL wrote: > Hey > I am looking for an algo for the largest sequence search in the two list. > > Example : list a accepts some say 'm' numbers. list b accept says 'n' > numbers. I want to look for the largest same sequence between the two list > and then display it. I tried out but failed to do so. > Say A=[11,23,45,21,63,56,78,32] > B=[56,78,11,23,45,21,111,234,56543] > > There are two similar sequence matching over here [11,23] and [23,45,21] > i want to display second sequence because its larger in number. Plz help > Thanks in Advance :) The following is not particular efficient, but may be good enough if the sequences are not too long: def index(items, value): """Generate all occurences of `value` in `items`""" start = 0 while True: try: pos = items.index(value, start) except ValueError: break yield pos start = pos + 1 def matches(a, b): for i, x in enumerate(a): for k in index(b, x): for p, (s, t) in enumerate(zip(a[i:], b[k:])): if s != t: break yield a[i:i+p] if __name__ == "__main__": a = [11, 23, 45, 21, 63, 56, 78, 32] b = [56, 78, 11, 23, 45, 21, 111, 234, 56543] print(max(matches(a, b), key=len)) print(sorted(matches(a, b))) ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Algorithm for sequence matching
Hi Ankur, On 2 July 2011 21:30, ANKUR AGGARWAL wrote: > Hey > I am looking for an algo for the largest sequence search in the two list. > > Example : list a accepts some say 'm' numbers. list b accept says 'n' > numbers. I want to look for the largest same sequence between the two list > and then display it. I tried out but failed to do so. > Say A=[11,23,45,21,63,56,78,32] > B=[56,78,11,23,45,21,111,234,56543] > > There are two similar sequence matching over here [11,23] and > [11,23,45,21] i want to display second sequence because its larger in > number. Plz help > > OK, so what if A = [1,4,2,7,4,6] and B = [4,9,10,11,12,14,17,4]? Would you consider [4,4] a valid answer to your question? It is a common subsequence, albeit not of concescutive elements? Walter ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Algorithm for sequence matching
Just to clarify further: On 2 July 2011 23:46, Walter Prins wrote: > On 2 July 2011 21:30, ANKUR AGGARWAL wrote: > >> Example : list a accepts some say 'm' numbers. list b accept says 'n' >> numbers. I want to look for the largest same sequence between the two list >> and then display it. I tried out but failed to do so. >> Say A=[11,23,45,21,63,56,78,32] >> B=[56,78,11,23,45,21,111,234,56543] >> >> There are two similar sequence matching over here [11,23] and >> [11,23,45,21] i want to display second sequence because its larger in >> number. Plz help >> > > OK, so what if A = [1,4,2,7,4,6] and B = [4,9,10,11,12,14,17,4]? Would you > consider [4,4] a valid answer to your question? It is a common subsequence, > albeit not of concescutive elements? > There is a difference between a sub*sequence* and a sub*string*. Strictly speaking, a *subsquence* is a sequence that can be derived from another sequence by deleting some of the elements from the other sequence. The result thus retains the ordering from the original but the elements need not have been consecutive elements. A *substring* on the other hand implies consecutive elements. I'm trying to make sure I understand your question, and whether you're really after the longest common subsequence (LCS) or longest common substring. My question above thus are trying to establish which of the two cases you're really after. Obviously the answer will be different depending on what you really want. Regards Walter ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Blackjack Betting
Each player needs to be able to bet
# Blackjack
# From 1 to 7 players compete against a dealer
import cards, games
class BJ_Card(cards.Card):
""" A Blackjack Card. """
ACE_VALUE = 1
@property
def value(self):
if self.is_face_up:
v = BJ_Card.RANKS.index(self.rank) + 1
if v > 10:
v = 10
else:
v = None
return v
class BJ_Deck(cards.Deck):
""" A Blackjack Deck. """
def populate(self):
for suit in BJ_Card.SUITS:
for rank in BJ_Card.RANKS:
self.cards.append(BJ_Card(rank, suit))
class BJ_Hand(cards.Hand):
""" A Blackjack Hand. """
def __init__(self, name):
super(BJ_Hand, self).__init__()
self.name = name
def __str__(self):
rep = self.name + ":\t" + super(BJ_Hand, self).__str__()
if self.total:
rep += "(" + str(self.total) + ")"
return rep
@property
def total(self):
# if a card in the hand has value of None, then total is None
for card in self.cards:
if not card.value:
return None
# add up card values, treat each Ace as 1
t = 0
for card in self.cards:
t += card.value
# determine if hand contains an Ace
contains_ace = False
for card in self.cards:
if card.value == BJ_Card.ACE_VALUE:
contains_ace = True
# if hand contains Ace and total is low enough, treat Ace as 11
if contains_ace and t <= 11:
# add only 10 since we've already added 1 for the Ace
t += 10
return t
def is_busted(self):
return self.total > 21
class BJ_Player(BJ_Hand):
""" A Blackjack Player. """
def betting(stash):
try:
if stash > 0:
wager = int(input("\nHow much do you want to wager?: "))
if wager > bet.stash:
int(input("\n You can only wager what you have. How
much?: "))
elif wager < 0:
int(input("\n You can only wager what you have. How
much?: "))
except ValueError:
int(input("\n That's not valid! Choose a number: "))
def is_hitting(self):
response = games.ask_yes_no("\n" + self.name + ", do you want a hit?
(Y/N): ")
return response == "y"
def bust(self):
print(self.name, "busts.")
self.lose()
def lose(self):
print(self.name, "loses.")
def win(self):
print(self.name, "wins.")
def push(self):
print(self.name, "pushes.")
class BJ_Dealer(BJ_Hand):
""" A Blackjack Dealer. """
def is_hitting(self):
return self.total < 17
def bust(self):
print(self.name, "busts.")
def flip_first_card(self):
first_card = self.cards[0]
first_card.flip()
class BJ_Game(object):
""" A Blackjack Game. """
def __init__(self, names):
self.players = []
for name in names:
player = BJ_Player(name)
bet = BJ_Player(name).betting(stash = 10)
self.players.append(player)
self.dealer = BJ_Dealer("Dealer")
self.deck = BJ_Deck()
self.deck.populate()
self.deck.shuffle()
@property
def still_playing(self):
sp = []
for player in self.players:
if not player.is_busted():
sp.append(player)
return sp
def __additional_cards(self, player):
while not player.is_busted() and player.is_hitting():
self.deck.deal([player])
print(player)
if player.is_busted():
player.bust()
def play(self):
# deal initial 2 cards to everyone
self.deck.deal(self.players + [self.dealer], per_hand = 2)
self.dealer.flip_first_card()# hide dealer's first card
for player in self.players:
print(player)
print(self.dealer)
# deal additional cards to players
for player in self.players:
self.__additional_cards(player)
self.dealer.flip_first_card()# reveal dealer's first
if not self.still_playing:
# since all players have busted, just show the dealer's hand
print(self.dealer)
else:
# deal additional cards to dealer
print(self.dealer)
self.__additional_cards(self.dealer)
if self.dealer.is_busted():
# everyone still playing wins
for player in self.still_playing:
player.win()
else:
# compare each player still playing to dealer
for player in self.still_playing:
if player.total > self.dealer.total:
player.win()
elif player.total < self.dealer.total:
player.lose()
Re: [Tutor] problem reading script
> Suggestions for "a programmers font" gratefully received. DejaVu Sans Mono ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Algorithm for sequence matching
ANKUR AGGARWAL wrote: Hey I am looking for an algo for the largest sequence search in the two list. Example : list a accepts some say 'm' numbers. list b accept says 'n' numbers. I want to look for the largest same sequence between the two list and then display it. I tried out but failed to do so. Google is your friend. Please search for "longest common subsequence" and "longest common substring". You can add "algorithm" and "python" if you like. Wikipedia, for example, gives good algorithms for both problems, which can be adapted to Python. You might also like to look at the difflib module in the standard library, particularly the SequenceMatcher class. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Blackjack Betting
On Sat, Jul 2, 2011 at 4:47 PM, David Merrick wrote: > Each player needs to be able to bet > Traceback (most recent call last): > File "I:/Python/Python Source Code/chapter09/blackjackBetting.py", line > 204, in > main() > File "I:/Python/Python Source Code/chapter09/blackjackBetting.py", line > 196, in main > game = BJ_Game(names) > File "I:/Python/Python Source Code/chapter09/blackjackBetting.py", line > 120, in __init__ > bet = BJ_Player(name).betting(stash = 10) > TypeError: betting() got multiple values for keyword argument 'stash' > >>> > > The "(stash = 10)" syntax is only used in the function (or method, in this case) definition. It means that "stash" is optional: if no value is supplied for "stash", then it will be assigned a default value of 10. So you have choices: all of the following will invoke "betting" with "stash" having an initial value of 10. By value: > bet = BJ_Player(name).betting(10) > By passing a variable: > pari = 10 > bet = BJ_Player(name).betting(pari) > By default: > bet = BJ_Player(name).betting() > ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] problem with reading dns query
preetam shivaram wrote:
I have got a very simple idea in mind that i want to try out. Say i have a
browser, chrome for instance, and i want to search for the ip of the domain
name, say `www.google.com`. I use windows 7 and i have set the dns lookup
properties to manual and have given the address `127.0.0.1` where my server
(written in Python) is running. I started my server and i could see the dns
query like this:
It seems to me that you want to learn how to write your own DNS caching
server. To do that, you have to understand the DNS protocol. Start with
the Wikipedia article:
http://en.wikipedia.org/wiki/Domain_Name_System
We probably can't help you here, this is a list for learning Python, not
DNS. You might have more luck on the main Python list,
or news group But generally,
I would expect they'll give you the same advice I am giving: google is
your friend.
Search for "python DNS server" and you will find information that may be
useful to you.
More comments below:
WAITING FOR CONNECTION.
.recieved from : ('127.0.0.1', 59339)
"'~\\x17\\x01\\x00\\x00\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x03www\\x06google\\x02co\\x02in\\x00\\x00\\x01\\x00\\x01'"
The `waiting for connection` and the `received from` is from my server. How
do i get a breakdown form(a human readable form) of this message??
Define "human readable form".
The data you get includes binary bytes, that is, you are getting:
tilde
hex byte 17
hex byte 01
null byte
null byte
hex byte 01
etc.
How would you like the string to be displayed, if not with escaped hex
codes?
If you just print the string, the binary bytes will probably disappear
because your terminal doesn't show them. You can convert to human
readable form with escaped binary bytes using repr() like this:
>>> print s # non-printable characters don't print
~wwwgooglecoin
>>> print repr(s)
'~\x17\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\x03www\x06google\x02co\x02in\x00\x00\x01\x00\x01'
You could also try a hex dump, there are many recipes on the Internet.
Here's the first one I tried:
http://code.activestate.com/recipes/142812-hex-dumper/
>>> print(dump(s))
7E 17 01 00 00 01 00 00~...
0008 00 00 00 00 03 77 77 77.www
0010 06 67 6F 6F 67 6C 65 02.google.
0018 63 6F 02 69 6E 00 00 01co.in...
0020 00 01 ..
--
Steven
___
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