🌐 Mailman 3 March 2006 - Python-list - python.org

is Queue.Queue() serializable with cPickle?
by john peter March 1, 2006

March 1, 2006

i have the following custom extenstion of Queue.Queue() to save and load queue contents but I think there's a problem with it. Does anybody know qhether Queue.Queue() is pickle-able? if so, can I get sample code? If not, can anybody recommend a pickle-able Queue from another library that I might be able to use? Thank you for any help! Here's my "PersistentQueue" extension: import cPickle import Queue import os from os.path import * class PersistentQueue(Queue.Queue): def __init__(self, maxsize=0): #print "init" Queue.Queue.__init__(self,maxsize) def saveState(self, file): fullFilePath = join(os.getcwd(),'savedStates', file) #print fullFilePath f = open(fullFilePath, 'w') l = [] while not self.empty(): l.append(self.get()) cPickle.dump(l, f) f.close() def loadState(self, file): fullFilePath = join(os.getcwd(),'savedStates', file) #print fullFilePath f = open(fullFilePath) l = cPickle.load(f) f.close() for i in l: self.put(i) if __name__ == '__main__': q = PersistentQueue(20) q.loadState("q1.sav") print q.get() q.put("four") q.saveState("q1.sav") --------------------------------- Yahoo! Mail Use Photomail to share photos without annoying attachments.

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Re: PEP 354: Enumerations in Python
by roy＠panix.com March 1, 2006

March 1, 2006

Tim Chase <python.list(a)tim.thechases.com> wrote: >>> Do you anticipate having parameters like socket.AF_INET >>> that are currently integers, become enumeration members >>> in future releases? >> >> Since these are derived from values defined as integers >> in C, it's probably better to leave them that way. There >> may be code that relies on them being integers or having >> those integer values. > >I'd say that "because something is done in C, it's the best >way to do it in Python" is a bad line of reasoning :) If I >wanted C, I'd use C. The problem is that the C language binding in this case is simply exposing the even lower level operating system interface. At that level, the address family is indeed just an arbitrary integer. The socket man page on (for example) Solaris-9 says things like, "The currently understood formats are", and "If a protocol is specified by the caller, then it will be packaged into a socket level option request and sent to the underlying pro- tocol layers". You don't really know for sure if you used a valid value until the low-level protocol drivers look at the number you passed in. This doesn't sound like an enum to me. There are plenty of places where we pass around integers that would be better served by enums. Address families and protocol numbers in the socket interface just isn't one of them.

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Is Python a Zen language?
by John Coleman March 1, 2006

March 1, 2006

Greetings, I have a rough classification of languages into 2 classes: Zen languages and tool languages. A tool language is a language that is, well, a *tool* for programming a computer. C is the prototypical tool language. Most languages in the Algol family are tool languages. Visual Basic and Java are also tool languages. On the other hand, a Zen language is a language which is purported to transform your way of thinking about programming. Lisp, Scheme, Forth, Smalltalk and (maybe) C++ are Zen languages. Disciples acknowledge that it is difficult to pick up these languages but claim that, if you persevere, you sooner or later reach a state of computational satori in which it all makes sense. Interestingly enough, these languages often have books which approach scriptural status e.g. SICP for Scheme. So (assuming my classification makes sense) which is Python? The emphasis on simplicity and the beginner-friendly nature of it seems to put it in the tool category. On the other hand, the emphasis on the ONE TRUE WAY to accomplish most tasks and the tendency for participants in this newsgroup to criticize one another's code as being "unpythonic" seems to move it towards the Zen category. Of course, even tool languages have their idioms which the novice needs to pick up, so maybe this isn't decisive, but I detect an element of zeal in this newsgroup that I don't detect in (say) Excel VBA programming newsgroups. No value judgement is intended by my classification. There is no denying that Zen languages are often very powerful tools (for those who have reached satori) and that there is a Zen to really mastering, say, C. Personally, I have never been able to master any Zen language but can pick up tool languages fairly quickly, so I prefer tool languages. This is probably because I am not a programmer (I'm a mathematician who likes to program as a hobby and for numerical simulations) and so don't have the time to invest in picking up a Zen language. Hard-core hackers might presumably lean towards the Zen languages. Just curious -John Coleman

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Python Indentation Problems
by diffuser78＠gmail.com March 1, 2006

March 1, 2006

I am a newbie to Python. I am mainly using Eric as the IDE for coding. Also, using VIM and gedit sometimes. I had this wierd problem of indentation. My code was 100% right but it wont run because indentation was not right. I checked time and again but still no success. I rewrote the code over again in VI and it ran. Can you please explain whats the trick behind the correct indentation. Thanks

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Re: Problem solved: Re: time.sleep(1) sometimes runs for 200 seconds under windows
by Magnus Lycka March 1, 2006

March 1, 2006

Paul Probert wrote: > Thanks everyone for your help. > It was the "Abouttime.exe" program, a time synch utility. To get the > problem, you have to run it as a service, and possibly it has to have > trouble connecting to its time servers. It would cause time.sleep(1) to > sometimes block for 200 seconds. Not "about" 200 seconds but always > within 199 to 202 seconds. Very strange, but it is good to have the > problem gone. So did you understand what happened? Was the system call time.time() just hanging while abouttime.exe was synching time?

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Re: pysqlite problem
by bapolis＠gmail.com March 1, 2006

March 1, 2006

I tried using the path "c:\ex1.db" and it worked. I was using "ex1.db" before. Thanks everyone for the help. This is a great community and maybe next time I will ask a harder question :)

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pysqlite problem
by bapolis＠gmail.com March 1, 2006

March 1, 2006

Hello, I'm getting the following error: pysqlite2.dbapi2.OperationalError: no such table: tbl1 Here's my code: from pysqlite2 import dbapi2 as sqlite con = sqlite.connect(":memory:", detect_types=sqlite.PARSE_COLNAMES) cur = con.cursor() cur.execute("select * from tbl1") data = cursor.fetchall() for record in date: record[0], record[1] my installation versions: python 2.4.2 pysqlite 2.0.7 sqlite 3.3.4 I checked to make sure I have a table called tbl1. I don't understand what's going on. Any ideas?

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RE: pysqlite problem
by Tim Golden March 1, 2006

March 1, 2006

[bapolis(a)gmail.com] | my bad. that was the wrong code, here is my code: | | from pysqlite2 import dbapi2 as sqlite | con = sqlite.connect("ex1") | cur = con.cursor() | cur.execute("select * from tbl1") | print cur.fetchall() Just a thought... is the file containing your database called -- exactly -- ex1? It's not called ex1.db or something? Because sqlite will happily create a new database when you connect, and if it did, it would obviously not contain your table. TJG ________________________________________________________________________ This e-mail has been scanned for all viruses by Star. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk ________________________________________________________________________

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RE: pysqlite problem
by Tim Golden March 1, 2006

March 1, 2006

[bapolis(a)gmail.com] | I'm getting the following error: | | pysqlite2.dbapi2.OperationalError: no such table: tbl1 | | Here's my code: | | from pysqlite2 import dbapi2 as sqlite | con = sqlite.connect(":memory:", detect_types=sqlite.PARSE_COLNAMES) | cur = con.cursor() | cur.execute("select * from tbl1") It may be that you've misunderstood something here (or that I have). You appear to be attaching to a sqlite in-memory database which does not exist before you connect to it. Therefore you are guaranteed *not* to have a table called tbl1 unless you create it first. Have you missed out some code for the purposes of brevity? Or have you misunderstood what the :memory: pseudo-filename is for? TJG ________________________________________________________________________ This e-mail has been scanned for all viruses by Star. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk ________________________________________________________________________

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Modify the local scope inside a function
by Sandra-24 March 1, 2006

March 1, 2006

Is there a way in python to add the items of a dictionary to the local function scope? i.e. var_foo = dict['var_foo']. I don't know how many items are in this dictionary, or what they are until runtime. exec statements are difficult for debuggers to deal with, so as a workaround I built my code into a function and saved it in a .py file. The I load the .py file as a module and call the function instead. This works great, and it has the added advantage of precompiled versions of the code being saved as .pyc and .pyo files. (faster repeated execution) The only trouble was I execed inside a specially created scope dictionary containing various variables and functions that the code requires. I can't seem to figure out how to get this same effect inside the function. Right now I'm passing the dict as an argument to the function, but I can't modify locals() so it doesn't help me. Thanks, -Sandra

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