Re: "/a" is not "/a" ?
Paul Rubin wrote: > Steven D'Aprano writes: >> It is never >> correct to avoid using "is" when you need to compare for identity. > > When is it ever necessary to compare for identity? Is that a trick question? The obvious answer is, any time you need to. The standard library has dozens of tests like: something is None something is not None Various standard modules include comparisons like: if frame is self.stopframe: if value is not __UNDEF__: if b is self.exit: if domain is Absent: if base is object: if other is NotImplemented: if type(a) is type(b): although that last one is probably better written using isinstance() or issubclass(). I have no doubt that there are many more examples. Comparing by identity are useful for interning objects, for testing that singletons actually are singletons, for comparing functions with the same name, for avoiding infinite loops while traversing circular data structures, and for non-destructively testing whether two mutable objects are the same object or different objects. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
On Mar 7, 10:57 am, s...@pobox.com wrote: > Right. Again though, when newcomers conflate the concepts they can deceive > themselves into thinking "is" is just a faster "==". But _you_ only _just_ stated "It does have some (generally small) performance ramifications as well" and provided timing examples to show it. Without qualification. And you're wondering why these mythical newcomers might be confused... -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
s...@pobox.com wrote: > Steven> Mutable versus immutable is irrelevant. The complexity of the > Steven> object is irrelevant. The phase of the moon is irrelevant. The > Steven> *only* relevant factor is the programmer's intention: > > Which for a new user not familiar with the differing concepts of "is" and > "==" can lead to mistakes. Right. And for newbies unfamiliar with Python, they might mistakenly think that ^ is the exponentiation operator rather than **. So what do we do? Do we teach them what ^ actually is, or give them bad advice "Never call ^" and then watch them needlessly write their own exponentiation function? Do we then defend this terrible advice by claiming that nobody needs exponentiation? Or that only experts need it? Or that it's necessary to tell newbies not to use ^ because they're only newbies and can't deal with the truth? No, of course not. But that's what some of us are doing with regard to "is". Because *some* newbies are ignorant and use "is" for equality testing, we patronisingly decide that *all* newbies can't cope with learning what "is" really is for, give them bad advice, and thus ensure that they stay ignorant longer. > Steven> If you find it difficult to think of a reason for testing for > Steven> identity, you're right, there aren't many. Since it's rare to > Steven> care about identity, it should be rare to use "is". But in the > Steven> few times you do care about identity, the correct solution is > to Steven> use "is" no matter what sort of object it happens to be. It > Steven> really is that simple. > > Right. Again though, when newcomers conflate the concepts they can > deceive themselves into thinking "is" is just a faster "==". Then teach them the difference, don't teach them superstition. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Should I use stackless python or threads?
On Mar 7, 9:35 am, Minesh Patel wrote: > I need to monitor each directory for the latest install, take it and > go perform some tests on a specific machine. I would like these > testing tasks to run concurrently for the obvious reasons. There are two other options to consider: * greenlet, which has come out of the Stackless project: http://codespeak.net/py/dist/greenlet.html * circuits, which comes with an iNotify driver: http://trac.softcircuit.com.au/circuits/browser/circuits/lib/drivers/inotify_driver.py Both of these libraries favour concurrency over threading, I believe. -- http://mail.python.org/mailman/listinfo/python-list
Re: Help cleaning up some code
"andrew cooke" writes: > def copy(src, dst, name, quote_none=False): > value = src[name] > dst[name] = 'None' if quote_none and value is None else value def copy(src, dst, name, default=None): value = src[name] dst[name] = value if value is not None else default > copy(row, ad, name, quote_none=True) copy(row, ad, name, default='None') -- http://mail.python.org/mailman/listinfo/python-list
Re: Help cleaning up some code
Thanks a lot! that copy function is a really neat trick!
Yes the ni's are sorted, and yes the query SHOULD be the one to limit it to
just one set of ni's; however, i am having trouble implementing that in sql.
I am using sqlite3 atm and right now i have a very large select statment the
gets me what i want, i just dont know how to filter it again base on data
that is from the result itself. I THINK normally one would select into a
temporary table then filter it from there, but i am not sure.
On Fri, Mar 6, 2009 at 9:43 PM, andrew cooke wrote:
> odeits wrote:
> > I am looking to clean up this code... any help is much appreciated.
> > Note: It works just fine, I just think it could be done cleaner.
> >
> > The result is a stack of dictionaries. the query returns up to
> > STACK_SIZE ads for a user. The check which i think is very ugly is
> > putting another contraint saying that all of the ni have to be the
> > same.
> >
> > stack = []
> > rows = self.con.execute(adquerystring,(user,STACK_SIZE)).fetchall()
> > for row in rows:
> > ad = dict()
> > ad['ni'] = row['ni']
> > ad['adid'] = row['adid']
> > ad['rundateid'] = row['rundateid']
> > ad['rundate'] = row['rundate']
> > if row['city'] is None:
> > ad['city'] = 'None'
> > else:
> > ad['city'] = row['city']
> > if row['state'] is None:
> > ad['state'] = 'None'
> > else:
> > ad['state'] = row['state']
> > ad['status'] = row['status']
> > try:
> > if stack[0]['ni'] != ad['ni']:
> > break;
> > except IndexError:
> > pass
> > stack.append(ad)
>
> NI = 'ni'
>
> def copy(src, dst, name, quote_none=False):
> value = src[name]
> dst[name] = 'None' if quote_none and value is None else value
>
> stack = []
> for row in self.con.execute(adquerystring,(user,STACK_SIZE)).fetchall():
> ad = dict()
> for name in (NI, 'adid', 'rundateid', 'rundate', 'status'):
>copy(row, ad, name)
> for name in ('city', 'state'):
>copy(row, ad, name, quote_none=True)
> if stack and stack[0][NI] != ad[NI]:
>break
> stack.append(ad)
>
> but couldn't you change the query so that it only returns a single 'ni'?
>
> also, do you really want to break, or just skip the append? maybe you
> want:
>
> if not stack or stack[0]['ni'] == ad['ni']:
>stack.append(ad)
>
> or perhaps the 'ni' are sorted (in which case what you are doing makes
> some sense).
>
> andrew
>
>
> > --
> > http://mail.python.org/mailman/listinfo/python-list
> >
> >
>
>
>
--
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Re: Help cleaning up some code
odeits wrote:
> I am looking to clean up this code... any help is much appreciated.
> Note: It works just fine, I just think it could be done cleaner.
>
> The result is a stack of dictionaries. the query returns up to
> STACK_SIZE ads for a user. The check which i think is very ugly is
> putting another contraint saying that all of the ni have to be the
> same.
>
> stack = []
> rows = self.con.execute(adquerystring,(user,STACK_SIZE)).fetchall()
> for row in rows:
> ad = dict()
> ad['ni'] = row['ni']
> ad['adid'] = row['adid']
> ad['rundateid'] = row['rundateid']
> ad['rundate'] = row['rundate']
> if row['city'] is None:
> ad['city'] = 'None'
> else:
> ad['city'] = row['city']
> if row['state'] is None:
> ad['state'] = 'None'
> else:
> ad['state'] = row['state']
> ad['status'] = row['status']
> try:
> if stack[0]['ni'] != ad['ni']:
> break;
> except IndexError:
> pass
> stack.append(ad)
NI = 'ni'
def copy(src, dst, name, quote_none=False):
value = src[name]
dst[name] = 'None' if quote_none and value is None else value
stack = []
for row in self.con.execute(adquerystring,(user,STACK_SIZE)).fetchall():
ad = dict()
for name in (NI, 'adid', 'rundateid', 'rundate', 'status'):
copy(row, ad, name)
for name in ('city', 'state'):
copy(row, ad, name, quote_none=True)
if stack and stack[0][NI] != ad[NI]:
break
stack.append(ad)
but couldn't you change the query so that it only returns a single 'ni'?
also, do you really want to break, or just skip the append? maybe you want:
if not stack or stack[0]['ni'] == ad['ni']:
stack.append(ad)
or perhaps the 'ni' are sorted (in which case what you are doing makes
some sense).
andrew
> --
> http://mail.python.org/mailman/listinfo/python-list
>
>
--
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Re: how to prevent python import from looking into the current directory
On Mar 6, 1:54 am, Ben Finney wrote: > (Could you please set a valid email address for people to contact you > if necessary?) > > TP writes: > > I would like to prevent the loading of modules in the current > > directory. > > You will, I think, like the new distinction between “absolute” and > “relative” imports http://www.python.org/dev/peps/pep-0328/>. He might, but it won't help him with his problem. Relative imports aren't involved in this situation. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Re: wxPython fast and slow
iu2 wrote: Do you have any idea of what is going wrong? I think this might be related to the OS's process prioritization, focused Windows would get more priority than background window. -- http://mail.python.org/mailman/listinfo/python-list
Re: create boolean
On 2009-03-07, Rhodri James wrote: > On Fri, 06 Mar 2009 15:34:08 -, Grant Edwards wrote: > >> On 2009-03-06, Fencer wrote: >> >>> Hi, I need a boolean b to be true if the variable n is not >>> None and not an empty list, otherwise b should be false. >> >>> I ended up with: >> >>> b = n is not None and not not n >> >> I'd do it like this: >> >> b = (n is not None) and (n != []) > > The second comparison isn't actually necessary, since an > empty list is True and a non-empty one False. > >b = (n is not None) and n > > Putting the comparison in does make the code slightly less > "magic", though, so it's not a bad idea to do it! Putting in the second comparison in makes the code match the stated requirement. Otherwise you have to start making assumptions about what n might be besides None or the empty list. -- Grant -- http://mail.python.org/mailman/listinfo/python-list
Re: python image - ignore values in resize
Travis Kirstine wrote: I have be attempting to resize (downsample) a RGB image using the python image library resize function. Everything works fine but I would like to exclude black values 0,0,0 from the calculations. I have tried creating a alpha mask based on black values then performing the resize but that only create partially transparent tiles in the regions that had black values Crop the image first. -- http://mail.python.org/mailman/listinfo/python-list
Re: Should I use stackless python or threads?
Minesh Patel wrote: On Fri, Mar 6, 2009 at 3:16 PM, Jean-Paul Calderone wrote: On Fri, 6 Mar 2009 14:50:51 -0800, Minesh Patel wrote: I am trying to figure out the best approach to solve this problem: I want to poll various directories(can be run in the main thread). Once I notice a file has been added to any directory, I grab a lock, spawn a thread to go perform the necessary actions, and then release the lock. That's not a description of a problem. That's a description of a potential solution. What problem are you trying to solve? I have a build system that is outputting various forms of installations in a particular directory structure, e.g. /pxe-installs, /iso-install, /dd-installs, etc... I need to monitor each directory for the latest install, take it and go perform some tests on a specific machine. I would like these testing tasks to run concurrently for the obvious reasons. Why not use subprocess. For each update to the directory you spawn a new subprocess. -- http://mail.python.org/mailman/listinfo/python-list
Help cleaning up some code
I am looking to clean up this code... any help is much appreciated. Note: It works just fine, I just think it could be done cleaner. The result is a stack of dictionaries. the query returns up to STACK_SIZE ads for a user. The check which i think is very ugly is putting another contraint saying that all of the ni have to be the same. stack = [] rows = self.con.execute(adquerystring,(user,STACK_SIZE)).fetchall() for row in rows: ad = dict() ad['ni'] = row['ni'] ad['adid'] = row['adid'] ad['rundateid'] = row['rundateid'] ad['rundate'] = row['rundate'] if row['city'] is None: ad['city'] = 'None' else: ad['city'] = row['city'] if row['state'] is None: ad['state'] = 'None' else: ad['state'] = row['state'] ad['status'] = row['status'] try: if stack[0]['ni'] != ad['ni']: break; except IndexError: pass stack.append(ad) -- http://mail.python.org/mailman/listinfo/python-list
Re: where is the PyString_AsString in Python 3.0?
BigHand gmail.com> writes: > > Finally I got the results now. This did take me 10 hours to solve > this. the docs of 3.0.. > I hope this could help someone else: > const char *strExcType = PyBytes_AS_STRING(pyStr); > Py_XDECREF(str_exc_type); > Py_XDECREF(pyStr); You can't Py_DECREF() pyStr while holding on to strExcType because PyBytes_AS_STRING just yields a reference to the internal contents of the object. -- http://mail.python.org/mailman/listinfo/python-list
Re: retrieve traceback in embedded python of Python3.0?
On Mar 7, 11:40 am, BigHand wrote:
> Guys:
> I have a embedded python in MFC app. to execute a py script of a.py,
> the is only one line in a.py, it "a()" , normally ,excute this script
> file ,you will get a
> "the exception type is "
> "The exception value is name 'a' is not defined "
>
> Python3.0 with VS2005.
> here is the brief code:
> Py_Initialize();
> PyObject *m, *d, *v;
> m = PyImport_AddModule("__main__");
> d = PyModule_GetDict(m);
> v = PyRun_File(fp, pStr, Py_file_input, d, d); //~~~the py
> script is a.py
> PyObject *exc_type = NULL, *exc_value = NULL, *exc_tb = NULL;
> PyErr_Fetch(&exc_type, &exc_value, &exc_tb); //~~~after fetch , the
> exc_type, exc_value, exc_tb are not "NULL"
> PyObject * modTB = PyImport_ImportModule("traceback");
> PyObject* pyUStr = PyUnicode_FromString("format_exception");
> PyObject* listTB = PyObject_CallMethodObjArgs(modTB, pyUStr,
> exc_type, exc_value, exc_tb, NULL);
>
> in the PyObject_CallMethodObjArgs(modTB, pyUStr, exc_type, exc_value,
> exc_tb, NULL), I get modTB, pyUStr, exc_type, exc_value, exc_tb are
> not NULL, but the listTB is always NULL, I can retrieve the list...
>
> any body could enlight me?
it's "I can't retrieve the traceback list."
--
http://mail.python.org/mailman/listinfo/python-list
Re: retrieve traceback in embedded python of Python3.0?
On Mar 7, 11:40 am, BigHand wrote:
> Guys:
> I have a embedded python in MFC app. to execute a py script of a.py,
> the is only one line in a.py, it "a()" , normally ,excute this script
> file ,you will get a
> "the exception type is "
> "The exception value is name 'a' is not defined "
>
> Python3.0 with VS2005.
> here is the brief code:
> Py_Initialize();
> PyObject *m, *d, *v;
> m = PyImport_AddModule("__main__");
> d = PyModule_GetDict(m);
> v = PyRun_File(fp, pStr, Py_file_input, d, d); //~~~the py
> script is a.py
> PyObject *exc_type = NULL, *exc_value = NULL, *exc_tb = NULL;
> PyErr_Fetch(&exc_type, &exc_value, &exc_tb); //~~~after fetch , the
> exc_type, exc_value, exc_tb are not "NULL"
> PyObject * modTB = PyImport_ImportModule("traceback");
> PyObject* pyUStr = PyUnicode_FromString("format_exception");
> PyObject* listTB = PyObject_CallMethodObjArgs(modTB, pyUStr,
> exc_type, exc_value, exc_tb, NULL);
>
> in the PyObject_CallMethodObjArgs(modTB, pyUStr, exc_type, exc_value,
> exc_tb, NULL), I get modTB, pyUStr, exc_type, exc_value, exc_tb are
> not NULL, but the listTB is always NULL, I can retrieve the list...
>
> any body could enlight me?
it's "I can't retrieve the trace back list."
--
http://mail.python.org/mailman/listinfo/python-list
retrieve traceback in embedded python of Python3.0?
Guys:
I have a embedded python in MFC app. to execute a py script of a.py,
the is only one line in a.py, it "a()" , normally ,excute this script
file ,you will get a
"the exception type is "
"The exception value is name 'a' is not defined "
Python3.0 with VS2005.
here is the brief code:
Py_Initialize();
PyObject *m, *d, *v;
m = PyImport_AddModule("__main__");
d = PyModule_GetDict(m);
v = PyRun_File(fp, pStr, Py_file_input, d, d); //~~~the py
script is a.py
PyObject *exc_type = NULL, *exc_value = NULL, *exc_tb = NULL;
PyErr_Fetch(&exc_type, &exc_value, &exc_tb); //~~~after fetch , the
exc_type, exc_value, exc_tb are not "NULL"
PyObject * modTB = PyImport_ImportModule("traceback");
PyObject* pyUStr = PyUnicode_FromString("format_exception");
PyObject* listTB = PyObject_CallMethodObjArgs(modTB, pyUStr,
exc_type, exc_value, exc_tb, NULL);
in the PyObject_CallMethodObjArgs(modTB, pyUStr, exc_type, exc_value,
exc_tb, NULL), I get modTB, pyUStr, exc_type, exc_value, exc_tb are
not NULL, but the listTB is always NULL, I can retrieve the list...
any body could enlight me?
--
http://mail.python.org/mailman/listinfo/python-list
Re: Threading and tkinter
On Mar 6, 7:42 pm, a...@pythoncraft.com (Aahz) wrote:
> [posted and e-mailed -- please reply to the group]
>
> In article
> <492d5db9-3681-4ae8-827e-f2a4f66be...@v39g2000yqm.googlegroups.com>,
>
> gert wrote:
>
> >After reading the docs and seeing a few examples i think this should
> >work ?
>
> This is a bit late, and I don't have time to review your code, but you
> should see a good example here:
>
> http://www.pythoncraft.com/OSCON2001/index.html
> --
> Aahz (a...@pythoncraft.com) <*> http://www.pythoncraft.com/
>
> "All problems in computer science can be solved by another level of
> indirection." --Butler Lampson
Witch basically translate into stop being a smart ass and just do
this :)
from tkinter import *
def weegbrug():
with open('com1','r') as f:
for l in f:
v.set(l[2:-1])
root.after(500, weegbrug)
root = Tk()
v = StringVar()
v.set("0")
txt = Label(root, textvariable=v, width=800, height=600, bg="yellow",
font=("Helvetica", 300))
txt.pack(expand=YES, fill=BOTH)
root.title("weegbrug")
root.overrideredirect(1)
root.geometry("%dx%d+0+0" % (root.winfo_screenwidth(),
root.winfo_screenheight()))
root.after(500, weegbrug)
root.mainloop()
--
http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao, the official 1.0 version is released
>> Why this hostility? The guy has worked on an interesting piece of >> software and tries to promote it to people who are most probably >> interested in programming languages. What's wrong with that? > > Because there's no particular reason for it to be in a Python-specific > forum. Yes there is, for example I found it useful (I'm interested in dynamic languages but I'm only subscribed to c.l.p) maybe others too. Gave me a much needed 5 minutes of recreational reading of his website which was just about perfect while drinking my coffee during coffee break :) > The value of a Python-specific forum is directly reduced by the > amount of off-topic noise that occurs in it. Yes, but not everything that is off-topic is noise. > The hostility is because we need to kick the camel's nose of “just > one clearly off-topic discussion” out of the tent to avoid the whole > camel coming in. Are you seriously worried that c.l.p will be overtaken by zealous dao fans? Cheers, Daniel -- Psss, psss, put it down! - http://www.cafepress.com/putitdown -- http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao, the official 1.0 version is released
This is to announce the first official release of Dao. Dao is a simple yet powerful object-oriented programming language >>> So, you pimp your language in news groups for other languages? I see >>> your off topic post in 3 language groups I frequent, that's not the way >>> to get interest in your language. >> >> Why this hostility? > > Why your hostility to people asking questions and making comments and > statements in response to a boilerplate announcement? > >> The guy has worked on an interesting piece of >> software and tries to promote it to people who are most probably >> interested in programming languages. What's wrong with that? > > There are probably a hundred other 'interesting pieces of software' that > could be announced here. There are tons of 'interesting pieces of software' that are actually announced here. And there is nothing wrong with that. > What the OP make no attempt to do was craft a > post actually directed to this particular group. Something like 'It has > the following influences from Python...' or 'Here is how it compares to > Python...'. Either would have made it a communication rather than a > blind broadcast. A blind broadcast serves a purpose, namely if someone knows nothing about this language, he/she will get to know that it exists. This is a useful purpose especially because the probability that people wish to know about the existence of the OP's new language is quite high (I suppose) among c.l.p readers. For example they can go to the website and see how it was influenced by python or how it compares to it. > > Some >> people occasionally ask general computer/linux/IT/etc questions simply >> because they think that the probability of finding somebody among >> python list followers who knows the answer (and is willing to share >> his/her knowledge) is high and since the topic is >> computer/linux/IT/etc it's not super far from things which are >> explicitly on topic. > > Mostly those are people who have posted Python questions and comments > before and otherwise are people planning to implement the answer in > Python. > >> No need for any hatred or hostility towards people who write a new >> programming language, > > I did not see any such thing. The mild hostility was directed at the > act of blind spamming, which we have had more than enough of. Well, there are lots of OT postings but in my estimation those that mention another language generate more hostility than those that don't. I don't see any reason for this increased hostility relative to other OT postings, hence I made my remark. Cheers, Daniel -- Psss, psss, put it down! - http://www.cafepress.com/putitdown -- http://mail.python.org/mailman/listinfo/python-list
Re: where is the PyString_AsString in Python 3.0?
On Mar 7, 9:34 am, BigHand wrote: > On Mar 7, 3:50 am, Benjamin Peterson wrote: > > > BigHand gmail.com> writes: > > > > > There is no PyString_AsString. Everything > > >> string is unicode now. (PyUnicode API) > > > hello,Ben, > > > could you give me an example? I almost know the > > > PyUnicode API,but the > > > docs of 3.0 is too brief for me. > > > PyString_FromString -> PyUnicode_FromString > > PyString_Concat -> PyUnicode_Concat > > etc... > > > To get a char * you have to explicitly encode the string with > > PyUnicode_AsEncodedString. > > thanks Ben! Finally I got the results now. This did take me 10 hours to solve this. the docs of 3.0.. I hope this could help someone else: PyObject *exc_type = NULL, *exc_value = NULL, *exc_tb = NULL; PyErr_Fetch(&exc_type, &exc_value, &exc_tb); PyObject* str_exc_type = PyObject_Repr(exc_type); //Now a unicode object PyObject* pyStr = PyUnicode_AsEncodedString(str_exc_type, "utf-8", "Error ~"); const char *strExcType = PyBytes_AS_STRING(pyStr); Py_XDECREF(str_exc_type); Py_XDECREF(pyStr); Py_XDECREF(exc_type); Py_XDECREF(exc_value); Py_XDECREF(exc_tb); -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way of doing this?
"Gabriel Genellina" writes: > > for x in population: > > f = fitness(x) > > fap += [(f, x)] > > total += f > > return sorted(fap, reverse=True), total > ... > Environmentally friendly Pythoneers avoid using discardable > intermediate envelopes: > > fap.append((f, x)) I'd probably use: fap = list((fitness(x),x) for x in population) total = sum(x for x,y in fap) return sorted(fap, reverse=True), total -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way of doing this?
En Fri, 06 Mar 2009 21:31:01 -0200, mattia escribió: Thanks, I've found another solution here: http://www.obitko.com/tutorials/ genetic-algorithms/selection.php so here is my implementation: def get_fap(fitness, population): fap = [] total = 0 for x in population: f = fitness(x) fap += [(f, x)] total += f return sorted(fap, reverse=True), total Imagine you're working with someone side by side. You write a note in a piece of paper, put it into an envelope, and hand it to your co-worker. He opens the envelope, throws it away, takes the note and files it inside a folder right at the end. And you do this over and over. What's wrong in this story? Please save our trees! Don't waste so many envelopes - that's just what this line does: fap += [(f, x)] Environmentally friendly Pythoneers avoid using discardable intermediate envelopes: fap.append((f, x)) Please recycle! -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
image exclude values from resize
I've been downsampling RGB images using pil, but know I would like to exclude black 0,0,0 values from the resize calculations. I was hoping that applying a alapha mask to black areas and creating RGBA image then performing the resample would fix the issue but no such luck. any ideas? -- http://mail.python.org/mailman/listinfo/python-list
Re: create boolean
On Fri, 06 Mar 2009 15:34:08 -, Grant Edwards wrote: On 2009-03-06, Fencer wrote: Hi, I need a boolean b to be true if the variable n is not None and not an empty list, otherwise b should be false. I ended up with: b = n is not None and not not n I'd do it like this: b = (n is not None) and (n != []) The second comparison isn't actually necessary, since an empty list is True and a non-empty one False. b = (n is not None) and n Putting the comparison in does make the code slightly less "magic", though, so it's not a bad idea to do it! -- Rhodri James *-* Wildebeeste Herder to the Masses -- http://mail.python.org/mailman/listinfo/python-list
Re: where is the PyString_AsString in Python 3.0?
On Mar 7, 3:50 am, Benjamin Peterson wrote: > BigHand gmail.com> writes: > > > > There is no PyString_AsString. Everything > >> string is unicode now. (PyUnicode API) > > hello,Ben, > > could you give me an example? I almost know the > > PyUnicode API,but the > > docs of 3.0 is too brief for me. > > PyString_FromString -> PyUnicode_FromString > PyString_Concat -> PyUnicode_Concat > etc... > > To get a char * you have to explicitly encode the string with > PyUnicode_AsEncodedString. thanks Ben! -- http://mail.python.org/mailman/listinfo/python-list
Re: Bizarre import duplication.
En Fri, 06 Mar 2009 22:05:53 -0200, Richard Thomas escribió: Say I have a project like this: ./run.py ./package/__init__.py ./package/mod1.py ./package/subpackage/__init__.py ./package/subpackage/mod2.py ./package/subpackage/mod3.py And suppose that "." and "package" (or their absolute paths) are in sys.path. That's a mistake. Never put redundant directories in sys.path. In this case, mod1 is reachable as "package.mod1" (from the "." entry in sys.path) and also as "mod1" (from the "package" entry). That must not happen - module names *must* be unique (here, "module name" means "sequence of package names plus the final file name", starting at some entry in sys.path) Usually there is no need (and it's not even convenient) to put a package in sys.path -- the directory *containing* the package should be listed instead. In this case, it is ".". Now mod1.py and mod2.py both contain this: from subpackage import mod3 In this very particular case, the two references to mod3 are separate initialisations of mod3.py. This can't be the intended behaviour, its maybe a little contrived but I found myself want to set it up this way so it can't be outside possibility. Using a relative import (and enabling absolute imports by default, by using: from __future__ import absolute_imports) is somewhat safer, but you can still confuse the complicated import machinery if you put redundant entries in sys.path -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Gary Herron wrote: >>> Newbies: Never use "is" to compare anything. >> >> Worse and worse! Now you're actively teaching newbies to write buggy >> code! > > Nonsense. Show me "newbie" level code that's buggy with "==" but > correct with "is". What's "newbie" level code? What does that even *mean*? There's no sandbox for newbies to play in -- their code runs in the same environment as code written by experts. Newbies can import modules written by experts and use their code: any object, no matter how complex, might find itself imported and used by a newbie. Sometimes code written by newbies might even find its way into code used by experts. But regardless of that, the point is, what's your motivation in giving advice to newbies? Do you want them to learn correct coding techniques, or to learn voodoo programming and superstition? If you want them to learn correct coding, then teach them the difference between identity and equality. If you want them to believe superstitions, then continue telling them never to use "is" without qualifications. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Steven> Mutable versus immutable is irrelevant. The complexity of the Steven> object is irrelevant. The phase of the moon is irrelevant. The Steven> *only* relevant factor is the programmer's intention: Which for a new user not familiar with the differing concepts of "is" and "==" can lead to mistakes. Steven> If you find it difficult to think of a reason for testing for Steven> identity, you're right, there aren't many. Since it's rare to Steven> care about identity, it should be rare to use "is". But in the Steven> few times you do care about identity, the correct solution is to Steven> use "is" no matter what sort of object it happens to be. It Steven> really is that simple. Right. Again though, when newcomers conflate the concepts they can deceive themselves into thinking "is" is just a faster "==". Skip -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
On 2009-03-06 18:29, Paul Rubin wrote: Steven D'Aprano writes: It is never correct to avoid using "is" when you need to compare for identity. When is it ever necessary to compare for identity? Caches of arbitrary objects. When checking if an object (which may be have an arbitrarily perverse __eq__) is None. Or a specifically constructed sentinel value. Checking for cycles in a data structure that defines __eq__. -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
s...@pobox.com wrote: > Of course, the more complex the objects you are comparing the > stronger the recommendation agaist using 'is' to compare two objects. Why is there so much voodoo advice about "is"? Is object identity really such a scary concept that people are frightened of it? Mutable versus immutable is irrelevant. The complexity of the object is irrelevant. The phase of the moon is irrelevant. The *only* relevant factor is the programmer's intention: If you want to test whether two objects have the same value (equality), the correct way to do it is with "==". If you want to test whether two objects are actually one and the same object, that is, they exist at the same memory location (identity), the correct way to do it is with "is". If you find it difficult to think of a reason for testing for identity, you're right, there aren't many. Since it's rare to care about identity, it should be rare to use "is". But in the few times you do care about identity, the correct solution is to use "is" no matter what sort of object it happens to be. It really is that simple. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Steven D'Aprano writes: > It is never > correct to avoid using "is" when you need to compare for identity. When is it ever necessary to compare for identity? -- http://mail.python.org/mailman/listinfo/python-list
Re: uniqueness of temporary files generated by tempfile
Catherine Moroney wrote: Are the temporary filenames generated by the tempfile module guaranteed to be unique? I suspect this answers your question... Emile >>> import tempfile >>> help(tempfile) Help on module tempfile: NAME tempfile - Temporary files. FILE c:\python25\lib\tempfile.py DESCRIPTION This module provides generic, low- and high-level interfaces for creating temporary files and directories. The interfaces listed as "safe" just below can be used without fear of race conditions. Those listed as "unsafe" cannot, and are provided for backward compatibility only. -- http://mail.python.org/mailman/listinfo/python-list
Re: Asking for prophecy
Stefan Spoettl wrote: In the pass it was always a good idea to use the newest Python verison for starting the development of a new application. First one could benefit from the additional features and second one could be sure that the community would have been passing during development. Nowadays we have at least three Python versions (2.5, 2.6, 3.0) on our machines and - damned! - I really don’t know which version I should use for my next development. The Unix-like systems as much as the major part of well maintained third party libraries are remaining "penetrantly" on 2.5. Why the vangard of the community don’t like to use at least 2.6 for bridging to the future Python? Is this the mutiny against the empery of the BDFL or is the vangard just asking for some more time? If I want to attest my personal attachment to the king by using 3.0, what will happen? Will I be deserted someday? It typically takes about a year before *most* 3-rd party libs have been converted. Windows binaries for C extentions tend to be slowest to arrive. Many people routinely skip 2.x.0 and wait to 2.x.1 both to skip initial bugs and wait for libraries. I have no idea if 2.6 conversions are slower than usual or not. 3.0 conversion was expected to be a bit slower. On the other hand, it is an opportunity to increase mindshare for libs which do make the conversion. I expect usage of Py3 will increase noticeably when 3.1 comes out in a few months with some notable fixes and improvements. I think there is at least half a chance that 2.7, which should arrive with 3.2, will be the last 2.x version. In the meanwhile, use whichever one meets your needs. I am currently using 3.0, but have 2.5 loaded in case I want to do something that needs 3rd-party libs before they are available for 3.x. Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: Parsing/Crawler Questions - solution
So, it sounds like your update means that it is related to a specific url. I'm curious about this issue myself. I've often wondered how one could properly crawl an AJAX-ish site when you're not sure how quickly the data will be returned after the page has been. John, your advice has really helped me. Bruce / anyone else, have you had any further experience with this type of parsing / crawling? On Mar 5, 2:50 pm, "bruce" wrote: > hi john... > > update... > > further investigation has revealed that apparently, for some urls/sites, the > server serves up pages that take awhile to be fetched... this appears to be > a potential problem, in that it appears that the parsescript never gets > anything from the python mech/urllib read function. > > the curious issue is that i can run a single test script, pointing to the > url, and after a bit of time.. the resulting content is fetched/downloaded > correctly. by the way, i can get the same results in my test browsing > environment, if i start it with only a subset of the urs that i've been > using to test the app. > > hmm... might be a resource issue, a timing issue,.. or something else... > hmmm... > > thanks > > again the problem i'm facing really has nothing to do with a specific > url... the app i have for the usc site works... > > but for any number of reasons... you might get different results when > running the app.. > -the server could be screwed up.. > -data might be cached > -data might be changed, and not updated.. > -actual app problems... > -networking issues... > -memory corruption issues... > -process constraint issues.. > -web server overload.. > -etc... > > the assumption that most people appear to make is that if you create a > parser, and run and test it once.. then if it gets you the data, it's > working.. when you run the same app.. 100s of times, and you're slamming the > webserver... then you realize that that's a vastly different animal than > simply running a snigle query a few times... > > so.. nope, i'm not running the app and getting data from a dynamic page that > hasn't finished uploading/creating the content.. > > but what my analysis is showing, not only for the usc, but for others as > well.. is that there might be differences in what gets returned... > > which is where a smoothing algorithmic approach appears to be workable.. > > i've been starting to test this approach, and it actually might have a > chance of working... > > so.. as i've stated a number of times.. focusing on a specific url isn't the > issue.. the larger issue is how you can > programatically/algorithmically/automatically, be reasonably ensured that > what you have is exactly what's on the site... > > ain't screen scraping fun!!! > > -Original Message- > From: python-list-bounces+bedouglas=earthlink@python.org > > [mailto:python-list-bounces+bedouglas=earthlink@python.org]on Behalf > Of John Nagle > Sent: Thursday, March 05, 2009 10:54 AM > To: python-l...@python.org > Subject: Re: Parsing/Crawler Questions - solution > > Philip Semanchuk wrote: > > On Mar 5, 2009, at 12:31 PM, bruce wrote: > > >> hi.. > > >> the url i'm focusing on is irrelevant to the issue i'm trying to solve at > >> this time. > > > Not if we're to understand the situation you're trying to describe. From > > what I can tell, you're saying that the target site displays different > > results each time your crawler visits it. It's as if e.g. the site knows > > about 100 courses but only displays 80 randomly chosen ones to each > > visitor. If that's the case, then it is truly bizarre. > > Agreed. The course list isn't changing that rapidly. > > I suspect the original poster is doing something like reading the DOM > of a dynamic page while the page is still updating, running a browser > in a subprocess. Is that right? > > I've had to deal with that in Javascript. My AdRater browser plug-in > (http://www.sitetruth.com/downloads) looks at Google-served ads and > rates the advertisers. There, I have to watch for page-change events > and update the annotations I'm adding to ads. > > But you don't need to work that hard here. The USC site is actually > querying a server which provides the requested data in JSON format. See > > http://web-app.usc.edu/soc/dev/scripts/soc.js > > Reverse-engineer that and you'll be able to get the underlying data. > (It's an amusing script; many little fixes to data items are performed, > something that should have been done at the database front end.) > > The way to get USC class data is this: > > 1. Start here: "http://web-app.usc.edu/soc/term_20091.html"; > 2. Examine all the department pages under that page. > 3. On each page, look for the value of "coursesrc", like this: > var coursesrc = '/ws/soc/api/classes/aest/20091' > 4. For each "coursesrc" value found, construct a URL like this: > http://web-app.usc.edu/ws/soc/api/classes/aest/20091 > 5. Read that URL. This will return the departmen
Re: ANN: Dao, the official 1.0 version is released
Daniel Fetchinson writes: > Why this hostility? The guy has worked on an interesting piece of > software and tries to promote it to people who are most probably > interested in programming languages. What's wrong with that? Because there's no particular reason for it to be in a Python-specific forum. The value of a Python-specific forum is directly reduced by the amount of off-topic noise that occurs in it. The hostility is because we need to kick the camel's nose of “just one clearly off-topic discussion” out of the tent to avoid the whole camel coming in. -- \“I fly Air Bizarre. You buy a combination one-way round-trip | `\ticket. Leave any Monday, and they bring you back the previous | _o__) Friday. That way you still have the weekend.” —Steven Wright | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Bizarre import duplication.
Say I have a project like this: ./run.py ./package/__init__.py ./package/mod1.py ./package/subpackage/__init__.py ./package/subpackage/mod2.py ./package/subpackage/mod3.py And suppose that "." and "package" (or their absolute paths) are in sys.path. Now mod1.py and mod2.py both contain this: from subpackage import mod3 In this very particular case, the two references to mod3 are separate initialisations of mod3.py. This can't be the intended behaviour, its maybe a little contrived but I found myself want to set it up this way so it can't be outside possibility. Richard -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
On Mar 6, 12:23 pm, Gary Herron wrote: > Robert Kern wrote: > > On 2009-03-06 13:46, Gary Herron wrote: > >> Emanuele D'Arrigo wrote: > >>> Hi everybody, > > >>> while testing a module today I stumbled on something that I can work > >>> around but I don't quite understand. > > >> *Do NOT use "is" to compare immutable types.* **Ever! ** > > > Well, "foo is None" is actually recommended practice > > But since newbies are always falling into this trap, it is still a good > rule to say: > > Newbies: Never use "is" to compare immutable types. No it isn't, it's asinine advice that's not even a simpllified truth, it's just a lie. Newbies who don't understand the difference between "==" and "is" should not be using "is", for any object, immutable or mutable, aside from None (which, whether you like it or not, is idomatic Python). Everyone who's learned the difference between equality and same identity, including experts, should be using "is" only to test if some object is the same object they created themselves, or is an object guaranteed by a library or the langauge to never change, irrespective of whether the object is mutable or not. At no point on the learning curve is the distinction of when to use "is" or not ever mutability. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
uniqueness of temporary files generated by tempfile
Are the temporary filenames generated by the tempfile module guaranteed to be unique? I have a need to generate temporary files within an application, and I will have many instances of this application running as a sub-process (so I can submit them to a batch queue). Is there any danger of my different sub-processes accidentally generating the same filename, or does tempfile check for the existence of a similarly-named file before generating a filename? What's the recommended way of generating temporary filenames that are guaranteed to be unique even with multiple processes running simultaneously? Catherine -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
En Fri, 06 Mar 2009 19:31:02 -0200, Emanuele D'Arrigo escribió: a = "a" b = "a" a is b True a = "/a" <- same as above, except the forward slashes! b = "/a" <- same as above, except the forward slashes! a is b False So, it appears that in the first case a and b are names to the same string object, while in the second case they are to two separate objects. Why? What's so special about the forward slash that cause the two "/a" strings to create two separate objects? Is this an implementation-specific issue? With all the answers you got, I hope you now understand that you put the question backwards: it's not "why aren't a and b the very same object in the second case?" but "why are they the same object in the first case?". Two separate expressions, involving two separate literals, don't *have* to evaluate as the same object. Only because strings are immutable the interpreter *may* choose to re-use the same string. But Python would still be Python even if all those strings were separate objects (although it would perform a lot slower!) -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
Re: searching for an easy library to create OpenOffice spreadsheets
Krishnakant wrote: Hello all, I am looking out for a python library which does the followingg. 1, create and manipulate openoffice spreadsheets. OpenOffice, by default, creates ODF -- Open Document Format -- documents as zipped xml subdocuments. Ooo is just one of many programs that work with them. One can access the actual xml with any decent zip program, such as 7zip. 2, allow for cell formatting including merging cells. 3, allow for colouring cells and formatting data as bold italics etc. 4, alignment of data should be possible. I looked at ooolib but did not find a method for merging cells. any ideas? odf2py? Have not used it yet. To get an idea of how to do what you want to do, create a simple spreadsheet with merged and formatted cells with OOoCalc and then look at the resulting xml rendition. tjr -- http://mail.python.org/mailman/listinfo/python-list
Re: How to replace the two last digits from an xml file?
On Mar 6, 3:31 pm, odeits wrote:
> On Mar 6, 11:53 am, awel wrote:
>
>
>
> > Hi,
>
> > I am trying to get a value from an xml file, increment it by 1,
> > replace by the new value and write another xml with the new value
> > inside.
>
> > I have found this code to get the line and it works but I have to do
> > everything manualy:
>
> > import re
> > lines = open("c:\\File1.xml").readlines()
> > for i in range(len(lines)):
> > if re.search('national.number', lines[i]):
> > lines[i] = lines[i].replace
> > ('01aaa02','01aaa03')
> > open("File2.xml","w").writelines(lines)
>
> > The goal I am trying to reach is to create 30 different xml.
>
> > Could someone help me?
>
> > Thanks
> > Al
>
> I would look into actually using an xml parser like lxml or the built
> in elementTree. You might run into some problems later on with the
> regex matching something unintended. Having said that..
>
> If you want to stick to regex i would pull out the number using a
> group, convert the number to a python type, increment then do the
> replace.
having dug a little deeper myself into the regular expressions in
python and grouping i stumbled onto this
http://www.amk.ca/python/howto/regex/regex.html#SECTION00052
Right above section 6. Common Problems there is an example of how to
change decimal numbers to hex... with a little tweek i believe it will
do exactly what you want.
Good Luck
--
http://mail.python.org/mailman/listinfo/python-list
Re: Reading Special Administration Console (SAC) in python
krishnakishore.nakarika...@gmail.com wrote: I want to read the Special Administration Console (SAC) output spew using python. Is it possible for me? It looks like that's just serial port I/O. If that doesn't get you going in the right direction it'll be a tough road... Emile -- http://mail.python.org/mailman/listinfo/python-list
Re: Should I use stackless python or threads?
On Fri, Mar 6, 2009 at 3:16 PM, Jean-Paul Calderone wrote: > On Fri, 6 Mar 2009 14:50:51 -0800, Minesh Patel wrote: >> >> I am trying to figure out the best approach to solve this problem: >> >> I want to poll various directories(can be run in the main thread). >> Once I notice a file has been added to any directory, I grab a lock, >> spawn a thread to go perform the necessary actions, and then release >> the lock. > > That's not a description of a problem. That's a description of a potential > solution. What problem are you trying to solve? > I have a build system that is outputting various forms of installations in a particular directory structure, e.g. /pxe-installs, /iso-install, /dd-installs, etc... I need to monitor each directory for the latest install, take it and go perform some tests on a specific machine. I would like these testing tasks to run concurrently for the obvious reasons. Thanks again for the help, Minesh -- http://mail.python.org/mailman/listinfo/python-list
Re: How to replace the two last digits from an xml file?
On Mar 6, 11:53 am, awel wrote:
> Hi,
>
> I am trying to get a value from an xml file, increment it by 1,
> replace by the new value and write another xml with the new value
> inside.
>
> I have found this code to get the line and it works but I have to do
> everything manualy:
>
> import re
> lines = open("c:\\File1.xml").readlines()
> for i in range(len(lines)):
> if re.search('national.number', lines[i]):
> lines[i] = lines[i].replace
> ('01aaa02','01aaa03')
> open("File2.xml","w").writelines(lines)
>
> The goal I am trying to reach is to create 30 different xml.
>
> Could someone help me?
>
> Thanks
> Al
I would look into actually using an xml parser like lxml or the built
in elementTree. You might run into some problems later on with the
regex matching something unintended. Having said that..
If you want to stick to regex i would pull out the number using a
group, convert the number to a python type, increment then do the
replace.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way of doing this?
Il Fri, 06 Mar 2009 14:13:47 -0800, Scott David Daniels ha scritto:
> mattia wrote:
>> Here is my last shot, where I get rid of all the old intermediate
>> functions:
>>
>> def selection(fitness, population):
>> lp = len(population)
>> roulette_wheel = []
>> for x in population:
>> roulette_wheel += [x]*fitness(x)
>> selected_population = [[]]*lp
>> selected_population[:2] = sorted(population, key=fitness,
>> reverse=True)[:2]
>> selected_population[2:] = [choice(roulette_wheel) for _ in range
>> (lp-2)]
> Try something like this to choose likely couples:
>
> import random
> import bisect
>
> def choose_pairs(fitness_population, decider=random):
> '''Pick and yield pairs weighted by fitness for crossing.
>
> We assume weighted_population has fitness already calculated.
> decide is a parameter to allow testing. '''
> total = 0
> cumulative = []
> candidates = []
> for fitness, individual in set(fitness_population):
> # calculate total weights, extract real candidates if
> fitness > 0:
> total += fitness
> cumulative.append(total)
> candidates.append(individual)
> assert len(candidates) > 1
> while True:
> # pick a candidate by weight
> c0 = decider.random() * total
> first = bisect.bisect_left(cumulative, c0) if first:
> weighting = cumulative[first] - cumulative[first - 1]
> else:
> weighting = cumulative[0]
> # pick another distinct candidate by fitness c1 = choice =
> decider.random() * (total - weighting) if choice >=
> cumulative[first] - weighting:
> choice += weight # adjust to avoid selecting first
> second = bisect.bisect_left(cumulative, choice) yield
> candidates[first], candidates[second]
>
> --Scott David Daniels
> scott.dani...@acm.org
Thanks, I've found another solution here: http://www.obitko.com/tutorials/
genetic-algorithms/selection.php
so here is my implementation:
def create_chromosome(min, max, length):
return [randint(min, max) for i in range(length)]
def create_population(nelem, min, max, length):
# preconditions: nelem > 1 and nelem is even
if not nelem > 1:
nelem = 2
if not nelem%2 == 0:
print("The population must have an even number of elements.
Correcting...")
nelem += 1
return [create_chromosome(min, max, length) for i in range(nelem)]
def get_fap(fitness, population):
fap = []
total = 0
for x in population:
f = fitness(x)
fap += [(f, x)]
total += f
return sorted(fap, reverse=True), total
def my_rw():
list, tot = get_fap(sum, pop)
r = randint(0, tot-1)
i = 0
print(r)
for f, e in list:
i += f
print(i)
if i > r:
return e
return [] # never reached
if __name__ == "__main__":
pop = create_population(5, 0, 1, 10)
# selection_mat(sum, pop)
#print(rw(sum, pop))
list, tot = get_fap(sum, pop)
print(list)
print(tot)
for i in range(6):
print(my_rw())
--
http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao, the official 1.0 version is released
Daniel Fetchinson wrote: This is to announce the first official release of Dao. Dao is a simple yet powerful object-oriented programming language So, you pimp your language in news groups for other languages? I see your off topic post in 3 language groups I frequent, that's not the way to get interest in your language. Why this hostility? Why your hostility to people asking questions and making comments and statements in response to a boilerplate announcement? The guy has worked on an interesting piece of software and tries to promote it to people who are most probably interested in programming languages. What's wrong with that? There are probably a hundred other 'interesting pieces of software' that could be announced here. What the OP make no attempt to do was craft a post actually directed to this particular group. Something like 'It has the following influences from Python...' or 'Here is how it compares to Python...'. Either would have made it a communication rather than a blind broadcast. > Some people occasionally ask general computer/linux/IT/etc questions simply because they think that the probability of finding somebody among python list followers who knows the answer (and is willing to share his/her knowledge) is high and since the topic is computer/linux/IT/etc it's not super far from things which are explicitly on topic. Mostly those are people who have posted Python questions and comments before and otherwise are people planning to implement the answer in Python. No need for any hatred or hostility towards people who write a new programming language, I did not see any such thing. The mild hostility was directed at the act of blind spamming, which we have had more than enough of. Terry -- http://mail.python.org/mailman/listinfo/python-list
Re: Should I use stackless python or threads?
On Fri, 6 Mar 2009 14:50:51 -0800, Minesh Patel wrote: I am trying to figure out the best approach to solve this problem: I want to poll various directories(can be run in the main thread). Once I notice a file has been added to any directory, I grab a lock, spawn a thread to go perform the necessary actions, and then release the lock. That's not a description of a problem. That's a description of a potential solution. What problem are you trying to solve? -- Thanks for the help, Minesh Patel -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao, the official 1.0 version is released
Limin> Honest to say, there is no solid connection between Dao and Limin> Python. It's just that I had received some good suggestions and Limin> comments from these groups when I made a few previous Limin> announcements in these groups. So I guessed somebody might be Limin> interested in Dao, and thought it might be a good idea to Limin> announce it here again. Saying just that in your announcement would have been enough, in my opinion to establish the connection. It's just that there was no mention of Python at all in your announcement. So I asked. -- Skip Montanaro - s...@pobox.com - http://www.smontanaro.net/ -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Gary> *Do NOT use "is" to compare immutable types.* **Ever! ** The obvious followup question is then, "when is it ok to use 'is'?" Robert> Well, "foo is None" is actually recommended practice Indeed. It does have some (generally small) performance ramifications as well. Two trivial one-line examples: % python -m timeit -s 'x = None' 'x is None' 1000 loops, best of 3: 0.065 usec per loop % python -m timeit -s 'x = None' 'x == None' 1000 loops, best of 3: 0.121 usec per loop % python -m timeit -s 'x = object(); y = object()' 'x == y' 1000 loops, best of 3: 0.154 usec per loop % python -m timeit -s 'x = object(); y = object()' 'x is y' 1000 loops, best of 3: 0.0646 usec per loop I imagine the distinction grows if you implement a class with __eq__ or __cmp__ methods, but that would make the examples greater than one line long. Of course, the more complex the objects you are comparing the stronger the recommendation agaist using 'is' to compare two objects. Skip -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Emanuele D'Arrigo wrote: On 6 Mar, 19:46, Gary Herron wrote: It is an implementation choice (usually driven by efficiency considerations) to choose when two strings with the same value are stored in memory once or twice. In order for Python to recognize when a newly created string has the same value as an already existing string, and so use the already existing value, it would need to search *every* existing string whenever a new string is created. Clearly that's not going to be efficient. However, the C implementation of Python does a limited version of such a thing -- at least with strings of length 1. Gary, thanks for your reply: your explanation does pretty much answer my question. One thing I can add however is that it really seems that non-alphanumeric characters such as the forward slash make the difference, not just the number of characters. I.e. a = "aaa" b = "aaa" a is b True a = "/aaa" b = "/aaa" a is b False I just find it peculiar more than a nuisance, but I'll go to the blackboard and write 100 times "never compare the identities of two immutables". Thank you all! Unless you are *trying* to discern something about the implementation and its attempt at efficiencies. Here's several more interesting example: >>> 101 is 100+1 True >>> 1001 is 1000+1 False >>> 10*'a' is 5*'aa' True >>> 100*'a' is 50*'aa' False Gary Herron Manu -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Should I use stackless python or threads?
I am trying to figure out the best approach to solve this problem: I want to poll various directories(can be run in the main thread). Once I notice a file has been added to any directory, I grab a lock, spawn a thread to go perform the necessary actions, and then release the lock. -- Thanks for the help, Minesh Patel -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
> So, it appears that in the first case a and b are names to the same
> string object, while in the second case they are to two separate
> objects. Why?
This question is ambiguous:
a) Why does the Python interpreter behave this way?
(i.e. what specific algorithm produces this result?)
or
b) Why was the interpreter written to behave this way?
(i.e. what is the rationale for that algorithm?)
For a), the answer is in Object/codeobject.c:
/* Intern selected string constants */
for (i = PyTuple_Size(consts); --i >= 0; ) {
PyObject *v = PyTuple_GetItem(consts, i);
if (!PyString_Check(v))
continue;
if (!all_name_chars((unsigned char *)PyString_AS_STRING(v)))
continue;
PyString_InternInPlace(&PyTuple_GET_ITEM(consts, i));
}
So it interns all strings which only consist of name
characters.
For b), the rationale is that such string literals
in source code are often used to denote names, e.g.
for getattr() calls and the like. As all names are interned,
name-like strings get interned also.
> What's so special about the forward slash that cause the
> two "/a" strings to create two separate objects?
See above.
> Is this an implementation-specific issue?
Yes, see above.
Martin
--
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Re: "/a" is not "/a" ?
Steven D'Aprano wrote: Gary Herron wrote: Robert Kern wrote: ... Use "is" when you really need to compare by object identity and not value. But that definition is the *source* of the trouble. It is *completely* meaningless to newbies. Until one has experience in programming in general and experience in Python in particular, the difference between "object identity" and "value" is a mystery. Then teach them the difference, rather than give them bogus advice. So in order to lead newbies away from this *very* common trap they often fall into, it is still a valid rule to say Newbies: Never use "is" to compare immutable types. Look in the standard library, and you will see dozens of cases of first-quality code breaking your "valid" rule. Your rule is not valid. A better rule might be: Never use "is" to compare equality. Or even: Never use "is" unless you know the difference between identity and equality. Or even: Only use "is" on Tuesdays. At least that last rule is occasionally right (in the same way a stopped clock is right twice a day), while your rule is *always* wrong. It is never correct to avoid using "is" when you need to compare for identity. of even better Newbies: Never use "is" to compare anything. Worse and worse! Now you're actively teaching newbies to write buggy code! Nonsense. Show me "newbie" level code that's buggy with "==" but correct with "is". However, I do like your restatement of the rule this way: Never use "is" unless you know the difference between identity and equality. That warns newbies away from the usual pitfall, and (perhaps) won't offend those who seem to forget what "newbie" means. Gary Herron -- http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao, the official 1.0 version is released
> i agree it's not clear how this is related to python (although i can see > the influence), but it does look like a nice language. thanks. > > one thing i was surprised to find missing was that the discussion of types > doesn't include classes (the discussion of macros doesn't include types, Actually the documentation about types does not mean to explain the types in a systematic way. It just tries to explain how to practically use them implicitly and explicitly, and to point out where one should pay attention. Classes surely should be discussed, but it didn't come into my mind when I prepared the documentation. It will be discussed when I update the document. > but that is more understandable). i am wondering if you have hidden > problems related to co and contra variance of types (like in java > generics). I have paid attention to the variance of types in some situations, but I am not very sure if it is without problems. Until now, I still feel there are still many things to be improved in the typing system. It would not be surprising if there are hidden problems regarding this. > > also, why is "@" needed as well as yield? in python, the presence of > yield makes "@" implicit (i think). You are right. I will change this. Thank you for pointing out this. I am glad that, every time I announced the language in the python mailing list, I received good comments and suggestions more often than in other mailing lists and groups, that's why python mailing list is one of the first places coming into my mind when I plan for an announcement of Dao;) > > andrew > > Limin Fu wrote: > > Hi, > > > This is to announce the first official release of Dao. > > -- Limin Fu http://www.daovm.net -- http://mail.python.org/mailman/listinfo/python-list
Re: qt, gtk, wx for py3 ?
On 2009-03-03, Mike Driscoll wrote: > It should be noted that the port for 3.0 hasn't started yet for > wxPython and I'm not seeing anything about a port for PyQt either > on their website. On 2009-03-05, Peter Billam wrote: > I mailed riverbankcomputing about PyQt for Py3; Phil Thompson replied > > The next release of PyQt is planned for the end of this month. > > It *might* make it to that release. > which, *if* it happens, is not so far away. > But that still leaves Gtk and Wx... In the Gtk front, Johan Dahlin of gnome.org points me to: http://bugzilla.gnome.org/show_bug.cgi?id=566641 which looks promising... Regards, Peter -- Peter Billam www.pjb.com.auwww.pjb.com.au/comp/contact.html -- http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao, the official 1.0 version is released
>> This is to announce the first official release of Dao. >> >> Dao is a simple yet powerful object-oriented programming language > > So, you pimp your language in news groups for other languages? I see > your off topic post in 3 language groups I frequent, that's not the way > to get interest in your language. Why this hostility? The guy has worked on an interesting piece of software and tries to promote it to people who are most probably interested in programming languages. What's wrong with that? Some people occasionally ask general computer/linux/IT/etc questions simply because they think that the probability of finding somebody among python list followers who knows the answer (and is willing to share his/her knowledge) is high and since the topic is computer/linux/IT/etc it's not super far from things which are explicitly on topic. No need for any hatred or hostility towards people who write a new programming language, I bet many people on this list are interested in this kind of stuff. Cheers, Daniel -- Psss, psss, put it down! - http://www.cafepress.com/putitdown -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way of doing this?
Il Fri, 06 Mar 2009 18:46:44 -0300, andrew cooke ha scritto: > i have not been following this discussion in detail, so someone may have > already explained this, but it should not be necessary to actually > construct the roulette wheel to select values from it. what you are > doing is selecting from a list where the there are different > probabilities of selecting different entries. i am pretty sure that can > be done more efficiently than by constructing a new list with many more > entries whose aim is to simulate that (which is what the roulette wheel > seems to be in your code, if i have understood correctly). > > more precisely, i think you can adapt the trick used to select a line at > random from a file by scanning the file just once. > > sorry if i have misunderstood, > andrew Well, I believe that using the right distribution I can for sure find a better way for doing the roulette wheel selection. When I'll have enough time I'll pick up my statistics book. -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way of doing this?
mattia wrote: Here is my last shot, where I get rid of all the old intermediate functions: def selection(fitness, population): lp = len(population) roulette_wheel = [] for x in population: roulette_wheel += [x]*fitness(x) selected_population = [[]]*lp selected_population[:2] = sorted(population, key=fitness, reverse=True)[:2] selected_population[2:] = [choice(roulette_wheel) for _ in range (lp-2)] Try something like this to choose likely couples: import random import bisect def choose_pairs(fitness_population, decider=random): '''Pick and yield pairs weighted by fitness for crossing. We assume weighted_population has fitness already calculated. decide is a parameter to allow testing. ''' total = 0 cumulative = [] candidates = [] for fitness, individual in set(fitness_population): # calculate total weights, extract real candidates if fitness > 0: total += fitness cumulative.append(total) candidates.append(individual) assert len(candidates) > 1 while True: # pick a candidate by weight c0 = decider.random() * total first = bisect.bisect_left(cumulative, c0) if first: weighting = cumulative[first] - cumulative[first - 1] else: weighting = cumulative[0] # pick another distinct candidate by fitness c1 = choice = decider.random() * (total - weighting) if choice >= cumulative[first] - weighting: choice += weight # adjust to avoid selecting first second = bisect.bisect_left(cumulative, choice) yield candidates[first], candidates[second] --Scott David Daniels scott.dani...@acm.org -- http://mail.python.org/mailman/listinfo/python-list
doctest + shelve question
Hello list,
I have a question. I'm writing a simple object serialization module
using shelve to write arbitrary objects to a file (M.py). Now I have the
problem, that if I create a simple object in the doctest documentation
file M.txt like this:
>>> class tdata(object):
... def __init__(self, name):
... self.name = name
>>> tinst = tdata(u'foo')
and then run it with my module M:
>>> import M
>>> foo = M.serialize('/tmp/foo', tinst.name, tinst)
which calls:
class serialize(object):
def __init__(self, path, key, data):
db = shelve.open(path)
db[key.encode('utf-8')] = data
db.close()
then I get the following problem:
Failed example:
foo = M.serialize('/tmp/foo', tinst)
Exception raised:
Traceback (most recent call last):
File "/usr/lib/python2.5/doctest.py", line 1228, in __run
compileflags, 1) in test.globs
...
File "/usr/lib/python2.5/shelve.py", line 123, in __setitem__
p.dump(value)
PicklingError: Can't pickle : attribute lookup
__builtin__.tdata failed
If I do the same in the interactive interpreter, then it works fine.
Now, as I want to test an arbitrary data class, the doctest file is the
place to put the simple tdata class, but as far as I traced the problem,
it uses it's own namespace or something, and so does not work.
I'd like to keep a consistent doctest documentation here and not spawn
my project with additional test modules or similar.
Any idea on how I can make it work like as if it would be called from
the interactive interpreter? The documentation and Google were not too
helpful.
ps. Sys: Linux, Python: 2.5.2
thanks
--
Sebastian Bartos,
keyserevr: pgp.mit.edu
signature.asc
Description: This is a digitally signed message part
--
http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Emanuele D'Arrigo wrote: > So, it appears that in the first case a and b are names to the same > string object, while in the second case they are to two separate > objects. Why? What's so special about the forward slash that cause the > two "/a" strings to create two separate objects? Is this an > implementation-specific issue? Python special cases certain objects like str with one element or small ints from -10 to +256 for performance reasons. It's version and implementation specific and may change in the future. Do NOT rely on it! Christian -- http://mail.python.org/mailman/listinfo/python-list
Re: how to prevent python import from looking into the current directory
Benjamin Peterson wrote:
> While the solutions given by others in this thread will work, I think it
> is best policy to not name your own modules after stdlib ones. When I see
> "os" referenced in code, I assume it is the stdlib one, and don't want to
> be confused by the presence of your own module.
Yes, I have finally chosen this alternative: things are much simpler like
this.
Thanks
--
python -c "print ''.join([chr(154 - ord(c)) for c in '*9(9&(18%.\
9&1+,\'Z4(55l4('])"
"When a distinguished but elderly scientist states that something is
possible, he is almost certainly right. When he states that something is
impossible, he is very probably wrong." (first law of AC Clarke)
--
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Re: Is there a better way of doing this?
i have not been following this discussion in detail, so someone may have already explained this, but it should not be necessary to actually construct the roulette wheel to select values from it. what you are doing is selecting from a list where the there are different probabilities of selecting different entries. i am pretty sure that can be done more efficiently than by constructing a new list with many more entries whose aim is to simulate that (which is what the roulette wheel seems to be in your code, if i have understood correctly). more precisely, i think you can adapt the trick used to select a line at random from a file by scanning the file just once. sorry if i have misunderstood, andrew -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
On 6 Mar, 19:46, Gary Herron wrote: > It is an implementation choice (usually driven by efficiency considerations) > to choose when two strings with the same value are stored in memory once or > twice. In order for Python to recognize when a newly created string has the > same value as an already existing string, and so use the already existing > value, it would need to search *every* existing string whenever a new string > is created. Clearly that's not going to be efficient. However, the C > implementation of Python does a limited version of such a thing -- at least > with strings of length 1. Gary, thanks for your reply: your explanation does pretty much answer my question. One thing I can add however is that it really seems that non-alphanumeric characters such as the forward slash make the difference, not just the number of characters. I.e. >>> a = "aaa" >>> b = "aaa" >>> a is b True >>> a = "/aaa" >>> b = "/aaa" >>> a is b False I just find it peculiar more than a nuisance, but I'll go to the blackboard and write 100 times "never compare the identities of two immutables". Thank you all! Manu -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way of doing this?
Il Fri, 06 Mar 2009 22:28:00 +0100, Peter Otten ha scritto: > mattia wrote: > >> Il Fri, 06 Mar 2009 14:06:14 +0100, Peter Otten ha scritto: >> >>> mattia wrote: >>> Hi, I'm new to python, and as the title says, can I improve this snippet (readability, speed, tricks): def get_fitness_and_population(fitness, population): return [(fitness(x), x) for x in population] def selection(fitness, population): ''' Select the parent chromosomes from a population according to their fitness (the better fitness, the bigger chance to be selected) ''' selected_population = [] fap = get_fitness_and_population(fitness, population) pop_len = len(population) # elitism (it prevents a loss of the best found solution) # take the only 2 best solutions elite_population = sorted(fap) selected_population += [elite_population[pop_len-1][1]] + [elite_population[pop_len-2][1]] # go on with the rest of the elements for i in range(pop_len-2): # do something >>> >>> def selection1(fitness, population, N=2): >>> rest = sorted(population, key=fitness, reverse=True) best = >>> rest[:N] del rest[:N] >>> # work with best and rest >>> >>> >>> def selection2(fitness, population, N=2): >>> decorated = [(-fitness(p), p) for p in population] >>> heapq.heapify(decorated) >>> >>> best = [heapq.heappop(decorated)[1] for _ in range(N)] rest = [p >>> for f, p in decorated] >>> # work with best and rest >>> >>> Both implementations assume that you are no longer interested in the >>> individuals' fitness once you have partitioned the population in two >>> groups. >>> >>> In theory the second is more efficient for "small" N and "large" >>> populations. >>> >>> Peter >> >> Ok, but the fact is that I save the best individuals of the current >> population, than I'll have to choose the others elements of the new >> population (than will be N-2) in a random way. The common way is using >> a roulette wheel selection (based on the fitness of the individuals, if >> the total fitness is 200, and one individual has a fitness of 10, that >> this individual will have a 0.05 probability to be selected to form the >> new population). So in the selection of the best solution I have to use >> the fitness in order to get the best individual, the last individual >> use the fitness to have a chance to be selected. Obviously the old >> population anf the new population must have the same number of >> individuals. > > You're right, it was a bad idea. > > Peter Here is my last shot, where I get rid of all the old intermediate functions: def selection(fitness, population): lp = len(population) roulette_wheel = [] for x in population: roulette_wheel += [x]*fitness(x) selected_population = [[]]*lp selected_population[:2] = sorted(population, key=fitness, reverse=True)[:2] selected_population[2:] = [choice(roulette_wheel) for _ in range (lp-2)] -- http://mail.python.org/mailman/listinfo/python-list
Re: how to prevent python import from looking into the current directory
TP Paralleles.invalid> writes: > > Hi everybody, > > I would like to prevent the loading of modules in the current directory. > For example, if I have a personal module in the current directory > named "os", when I do "import os", I would like Python to import os > standard module, not my personal module of the current directory. > Is this possible? While the solutions given by others in this thread will work, I think it is best policy to not name your own modules after stdlib ones. When I see "os" referenced in code, I assume it is the stdlib one, and don't want to be confused by the presence of your own module. -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Thank you everybody for the contributions and sorry if I reawoke the recurring "is vs ==" issue. I -think- I understand how Python's object model works, but clearly I'm still missing something. Let me reiterate my original example without the distracting aspect of the "==" comparisons and the four variables: >>> a = "a" >>> b = "a" >>> a is b True >>> a = "/a" <- same as above, except the forward slashes! >>> b = "/a" <- same as above, except the forward slashes! >>> a is b False So, it appears that in the first case a and b are names to the same string object, while in the second case they are to two separate objects. Why? What's so special about the forward slash that cause the two "/a" strings to create two separate objects? Is this an implementation-specific issue? Manu -- http://mail.python.org/mailman/listinfo/python-list
python image - ignore values in resize
I have be attempting to resize (downsample) a RGB image using the
python image library resize function. Everything works fine but I
would like to exclude black values 0,0,0 from the calculations. I
have tried creating a alpha mask based on black values then performing
the resize but that only create partially transparent tiles in the
regions that had black values
im = Image.open('src.tif')
multi = im.split
mask = im.point(lambda i: i == 0 and 255)# get 0 values
mask = mask.convert('L')
mask = ImageChops.invert(mask) # make the 0 values 255 for transparency
out_im = Image.merge('RGBA', (multi[0], multi[1], multi[2], mask))
out_im = out_im.resize((100, 100), Image.ANTIALIAS)
out_im = out_im.convert('RGB')
out_im.save('dst.tif')
Any help would be great
--
Travis K.
Toronto, Canada
"She knows there's no success like failure
And that failure's no success at all."
-Bob Dylan-
--
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Re: ANN: Dao, the official 1.0 version is released
> > i agree it's not clear how this is related to python (although i can see > the influence), but it does look like a nice language. thanks. > > > one thing i was surprised to find missing was that the discussion of types > doesn't include classes (the discussion of macros doesn't include Actually the documentation about types does not mean to explain the types in a systematic way. It just tries to explain how to practically use them implicitly and explicitly, and to point out where one should pay attention. Classes surely should be discussed, but it didn't come into my mind when I prepared the documentation. It will be discussed when I update the document. > types, > but that is more understandable). i am wondering if you have hidden > problems related to co and contra variance of types (like in java > generics). I have paid attention to the variance of types in some situations, but I am not very sure if it is without problems. Until now, I still feel there are still many things to be improved in the typing system. It would not be surprising if there are hidden problems regarding this. > > also, why is "@" needed as well as yield? in python, the presence of > yield makes "@" implicit (i think). > You are right. I will change this. Thank you for pointing out this. I am glad that, every time I announced the language in the python mailing list, I received good comments and suggestions more often than in other mailing lists and groups, that's why python mailing list is one of the first places coming into my mind when I plan for an announcement of Dao;) > > andrew > > > Limin Fu wrote: > > Hi, > > > > This is to announce the first official release of Dao. > > > -- Limin Fu http://www.daovm.net -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a better way of doing this?
mattia wrote: > Il Fri, 06 Mar 2009 14:06:14 +0100, Peter Otten ha scritto: > >> mattia wrote: >> >>> Hi, I'm new to python, and as the title says, can I improve this >>> snippet (readability, speed, tricks): >>> >>> def get_fitness_and_population(fitness, population): >>> return [(fitness(x), x) for x in population] >>> >>> def selection(fitness, population): >>> ''' >>> Select the parent chromosomes from a population according to their >>> fitness (the better fitness, the bigger chance to be selected) ''' >>> selected_population = [] >>> fap = get_fitness_and_population(fitness, population) pop_len = >>> len(population) >>> # elitism (it prevents a loss of the best found solution) # take >>> the only 2 best solutions >>> elite_population = sorted(fap) >>> selected_population += [elite_population[pop_len-1][1]] + >>> [elite_population[pop_len-2][1]] >>> # go on with the rest of the elements for i in range(pop_len-2): >>> # do something >> >> def selection1(fitness, population, N=2): >> rest = sorted(population, key=fitness, reverse=True) best = rest[:N] >> del rest[:N] >> # work with best and rest >> >> >> def selection2(fitness, population, N=2): >> decorated = [(-fitness(p), p) for p in population] >> heapq.heapify(decorated) >> >> best = [heapq.heappop(decorated)[1] for _ in range(N)] rest = [p for >> f, p in decorated] >> # work with best and rest >> >> Both implementations assume that you are no longer interested in the >> individuals' fitness once you have partitioned the population in two >> groups. >> >> In theory the second is more efficient for "small" N and "large" >> populations. >> >> Peter > > Ok, but the fact is that I save the best individuals of the current > population, than I'll have to choose the others elements of the new > population (than will be N-2) in a random way. The common way is using a > roulette wheel selection (based on the fitness of the individuals, if the > total fitness is 200, and one individual has a fitness of 10, that this > individual will have a 0.05 probability to be selected to form the new > population). So in the selection of the best solution I have to use the > fitness in order to get the best individual, the last individual use the > fitness to have a chance to be selected. Obviously the old population anf > the new population must have the same number of individuals. You're right, it was a bad idea. Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Gary Herron wrote: >> Huh? How am I supposed to compare immutable types for identity then? Your >> bizarre instruction would prohibit: >> >> if something is None >> > > Just use: > > if something == None > > It does *exactly* the same thing. Wrong. "something is None" is a pointer comparison. It's blindingly fast, and it will only return True if something is the same object as None. Any other object *must* return False. "something == None" calls something.__eq__(None), which is a method of arbitrary complexity, which may cause arbitrary side-effects. It can have false positives, where objects with unexpected __eq__ methods may return True, which is almost certainly not the intention of the function author and therefore a bug. [...] > If they use a couple "something==None" instead of "something is None" > in their code while learning Python, it won't hurt, Apart from the subtle bugs they introduce into their code. > and they can change > their style when they understand the difference. And meanwhile they > will skip traps newbies fall into when they don't understand these > things yet. How about teaching them the right reasons for using "is" instead of giving them false information by telling them they should never use it? -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Gary Herron wrote: > Robert Kern wrote: ... >> Use "is" when you really need to compare by object identity and not >> value. > > But that definition is the *source* of the trouble. It is *completely* > meaningless to newbies. Until one has experience in programming in > general and experience in Python in particular, the difference between > "object identity" and "value" is a mystery. Then teach them the difference, rather than give them bogus advice. > So in order to lead newbies away from this *very* common trap they often > fall into, it is still a valid rule to say > > Newbies: Never use "is" to compare immutable types. Look in the standard library, and you will see dozens of cases of first-quality code breaking your "valid" rule. Your rule is not valid. A better rule might be: Never use "is" to compare equality. Or even: Never use "is" unless you know the difference between identity and equality. Or even: Only use "is" on Tuesdays. At least that last rule is occasionally right (in the same way a stopped clock is right twice a day), while your rule is *always* wrong. It is never correct to avoid using "is" when you need to compare for identity. > of even better > > Newbies: Never use "is" to compare anything. Worse and worse! Now you're actively teaching newbies to write buggy code! -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Steven D'Aprano wrote:
Gary Herron wrote:
Emanuele D'Arrigo wrote:
Hi everybody,
while testing a module today I stumbled on something that I can work
around but I don't quite understand.
*Do NOT use "is" to compare immutable types.***Ever! **
Huh? How am I supposed to compare immutable types for identity then? Your
bizarre instruction would prohibit:
if something is None
Just use:
if something == None
It does *exactly* the same thing.
But... I'm not (repeat NOT) saying *you* should do it this way.
I am saying that since newbies continually trip over incorrect uses of
"is", they should be warned against using "is" in any situation until
they understand the subtle nature or "is".
If they use a couple "something==None" instead of "something is None"
in their code while learning Python, it won't hurt, and they can change
their style when they understand the difference. And meanwhile they
will skip traps newbies fall into when they don't understand these
things yet.
Gary Herron
which is the recommended way to compare to None, which is immutable. The
standard library has *many* identity tests to None.
I would say, *always* use "is" to compare any type whenever you intend to
compare by *identity* instead of equality. That's what it's for. If you use
it to test for equality, you're doing it wrong. But in the very rare cases
where you care about identity (and you almost never do), "is" is the
correct tool to use.
It is an implementation choice (usually driven by efficiency
considerations) to choose when two strings with the same value are stored
in memory once or twice. In order for Python to recognize when a newly
created string has the same value as an already existing string, and so
use the already existing value, it would need to search *every* existing
string whenever a new string is created.
Not at all. It's quite easy, and efficient. Here's a pure Python string
constructor that caches strings.
class CachedString(str):
_cache = {}
def __new__(cls, value):
s = cls._cache.setdefault(value, value)
return s
Python even includes a built-in function to do this: intern(), although I
believe it has been removed from Python 3.0.
Clearly that's not going to be efficient.
Only if you do it the inefficient way.
However, the C implementation of Python does a limited version
of such a thing -- at least with strings of length 1.
No, that's not right. The identity test fails for some strings of length
one.
a = '\n'
b = '\n'
len(a) == len(b) == 1
True
a is b
False
Clearly, Python doesn't intern all strings of length one. What Python
actually interns are strings that look like, or could be, identifiers:
a = 'heresareallylongstringthatisjustmade' \
... 'upofalphanumericcharacterssuitableforidentifiers123_'
b = 'heresareallylongstringthatisjustmade' \
... 'upofalphanumericcharacterssuitableforidentifiers123_'
a is b
True
It also does a similar thing for small integers, currently something
like -10 through to 256 I believe, although this is an implementation
detail subject to change.
--
http://mail.python.org/mailman/listinfo/python-list
Re: A Simple Tkinter Control Program--Slight Problem
I like to see closure on a thread. This should do it. from Tkinter import * # Use of control variables and callbacks def mycallback(): print "User entered:" , e.get() print "Operation by 2 gives: ", e.get()*2, "and", v.get()*2 master = Tk() #v=StringVar() v=IntVar() print v,type(v) print v, type(v), type(v.get()) e = Entry(master,textvariable=v) e.pack() b = Button(master, text="Push to Print", width=10, command=mycallback) b.pack() e.focus_set() v.set(123) mainloop() -- W. eWatson (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Web Page: -- http://mail.python.org/mailman/listinfo/python-list
Re: This should be a simple question...
Steven D'Aprano wrote: > Steve Holden wrote: > >> If x and b are meant to be global than bite the bullet and *make* them >> global. > > Well, there's global, and there's global. > > There's global to a few functions in a module, there's global to > everything > in a module, and global to an entire application. They're not necessarily > the same thing. this is probably drifting a bit far from the original question, but i have used function scope to hide information "global" to a few functions. the idea is to use a factory function that generates them all. def factory(): a = 12 b = 34 def ifamultb(x): if a == x: return x * b else: return x def somethinelse(x): blah blah (ifamultb, somethinelse) = factory() that's off the top of my head. you might need to work around python's stupid scoping rules with hidden params: def ifamultb(x, a=a): etc andrew -- http://mail.python.org/mailman/listinfo/python-list
Re: This should be a simple question...
Steve Holden wrote: > If x and b are meant to be global than bite the bullet and *make* them > global. Well, there's global, and there's global. There's global to a few functions in a module, there's global to everything in a module, and global to an entire application. They're not necessarily the same thing. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Robert Kern wrote: On 2009-03-06 14:23, Gary Herron wrote: Robert Kern wrote: On 2009-03-06 13:46, Gary Herron wrote: Emanuele D'Arrigo wrote: Hi everybody, while testing a module today I stumbled on something that I can work around but I don't quite understand. *Do NOT use "is" to compare immutable types.* **Ever! ** Well, "foo is None" is actually recommended practice But since newbies are always falling into this trap, it is still a good rule to say: Newbies: Never use "is" to compare immutable types. and then later point out, for those who have absorbed the first rule: Experts: Singleton immutable types *may* be compared with "is", although normal equality with == works just as well. That's not really true. If my object overrides __eq__ in a funny way, "is None" is much safer. Use "is" when you really need to compare by object identity and not value. But that definition is the *source* of the trouble. It is *completely* meaningless to newbies. Until one has experience in programming in general and experience in Python in particular, the difference between "object identity" and "value" is a mystery. So in order to lead newbies away from this *very* common trap they often fall into, it is still a valid rule to say Newbies: Never use "is" to compare immutable types. of even better Newbies: Never use "is" to compare anything. This will help them avoid traps, and won't hurt their use of the language. If they get to a point that they need to contemplate using "is", then almost be definition, they are not a newbie anymore, and the rule is still valid. Gary Herron -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Emanuele D'Arrigo wrote: > Hi everybody, > > while testing a module today I stumbled on something that I can work > around but I don't quite understand. Why do you have to work around it? What are you trying to do that requires that two strings should occupy the same memory location rather than merely being equal? > Why c and d point to two different objects with an identical string > content rather than the same object? Why shouldn't they? -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Gary Herron wrote:
> Emanuele D'Arrigo wrote:
>> Hi everybody,
>>
>> while testing a module today I stumbled on something that I can work
>> around but I don't quite understand.
>>
>
> *Do NOT use "is" to compare immutable types.***Ever! **
Huh? How am I supposed to compare immutable types for identity then? Your
bizarre instruction would prohibit:
if something is None
which is the recommended way to compare to None, which is immutable. The
standard library has *many* identity tests to None.
I would say, *always* use "is" to compare any type whenever you intend to
compare by *identity* instead of equality. That's what it's for. If you use
it to test for equality, you're doing it wrong. But in the very rare cases
where you care about identity (and you almost never do), "is" is the
correct tool to use.
> It is an implementation choice (usually driven by efficiency
> considerations) to choose when two strings with the same value are stored
> in memory once or twice. In order for Python to recognize when a newly
> created string has the same value as an already existing string, and so
> use the already existing value, it would need to search *every* existing
> string whenever a new string is created.
Not at all. It's quite easy, and efficient. Here's a pure Python string
constructor that caches strings.
class CachedString(str):
_cache = {}
def __new__(cls, value):
s = cls._cache.setdefault(value, value)
return s
Python even includes a built-in function to do this: intern(), although I
believe it has been removed from Python 3.0.
> Clearly that's not going to be efficient.
Only if you do it the inefficient way.
> However, the C implementation of Python does a limited version
> of such a thing -- at least with strings of length 1.
No, that's not right. The identity test fails for some strings of length
one.
>>> a = '\n'
>>> b = '\n'
>>> len(a) == len(b) == 1
True
>>> a is b
False
Clearly, Python doesn't intern all strings of length one. What Python
actually interns are strings that look like, or could be, identifiers:
>>> a = 'heresareallylongstringthatisjustmade' \
... 'upofalphanumericcharacterssuitableforidentifiers123_'
>>>
>>> b = 'heresareallylongstringthatisjustmade' \
... 'upofalphanumericcharacterssuitableforidentifiers123_'
>>> a is b
True
It also does a similar thing for small integers, currently something
like -10 through to 256 I believe, although this is an implementation
detail subject to change.
--
Steven
--
http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
On 2009-03-06 14:23, Gary Herron wrote: Robert Kern wrote: On 2009-03-06 13:46, Gary Herron wrote: Emanuele D'Arrigo wrote: Hi everybody, while testing a module today I stumbled on something that I can work around but I don't quite understand. *Do NOT use "is" to compare immutable types.* **Ever! ** Well, "foo is None" is actually recommended practice But since newbies are always falling into this trap, it is still a good rule to say: Newbies: Never use "is" to compare immutable types. and then later point out, for those who have absorbed the first rule: Experts: Singleton immutable types *may* be compared with "is", although normal equality with == works just as well. That's not really true. If my object overrides __eq__ in a funny way, "is None" is much safer. Use "is" when you really need to compare by object identity and not value. -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Robert Kern wrote: On 2009-03-06 13:46, Gary Herron wrote: Emanuele D'Arrigo wrote: Hi everybody, while testing a module today I stumbled on something that I can work around but I don't quite understand. *Do NOT use "is" to compare immutable types.* **Ever! ** Well, "foo is None" is actually recommended practice But since newbies are always falling into this trap, it is still a good rule to say: Newbies: Never use "is" to compare immutable types. and then later point out, for those who have absorbed the first rule: Experts: Singleton immutable types *may* be compared with "is", although normal equality with == works just as well. Gary Herron -- http://mail.python.org/mailman/listinfo/python-list
Re: Asking for prophecy
On Mar 6, 1:23 pm, "andrew cooke" wrote: > 3 and 2.6 are compatible. so develop on 3, to make sure you don't use old > junk, and then switch to 2.6 if you need to. there are a few wrinkles in > doing so, but it is not a big problem. > > 3.0 is a nicer language. it's cleaner and more consistent. i think > important libraries will move there. Probably, but until gmpy is available for 3.0, 3.0 does not exist yet as far as I'm concerned. > no-one wants to do a perl. it's the > likely future and you can always jump back to 2.6 if needed. > > and in the long term, we will all die. > > andrew > > > > Stefan Spoettl wrote: > > In the pass it was always a good idea to use the newest Python verison for > > starting the development of a new application. First one could benefit > > from the additional features and second one could be sure that the > > community would have been passing during development. > > > Nowadays we have at least three Python versions (2.5, 2.6, 3.0) on our > > machines and - damned! - I really don't know which version I should use > > for my next development. The Unix-like systems as much as the major part > > of well maintained third party libraries are remaining "penetrantly" on > > 2.5. Why the vangard of the community don't like to use at least 2.6 for > > bridging to the future Python? Is this the mutiny against the empery of > > the BDFL or is the vangard just asking for some more time? If I want to > > attest my personal attachment to the king by using 3.0, what will happen? > > Will I be deserted someday? > > > Stefan-- > >http://mail.python.org/mailman/listinfo/python-list- Hide quoted text - > > - Show quoted text - -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Gary Herron wrote: Emanuele D'Arrigo wrote: Hi everybody, while testing a module today I stumbled on something that I can work around but I don't quite understand. *Do NOT use "is" to compare immutable types.***Ever! ** Then it should be a detected error to do so. John Nagle -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
On 2009-03-06 13:46, Gary Herron wrote: Emanuele D'Arrigo wrote: Hi everybody, while testing a module today I stumbled on something that I can work around but I don't quite understand. *Do NOT use "is" to compare immutable types.* **Ever! ** Well, "foo is None" is actually recommended practice -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: Indentations and future evolution of languages
2009/3/6 : > This is an interesting post, it shows me that fitness plateau where > design of Python syntax lives is really small, you can't design > something just similar: > > http://unlimitednovelty.com/2009/03/indentation-sensitivity-post-mortem.html I don't think the article is right that "it's silly to have some expression/statement groupings indentation based and some grouped by enclosing tokens" -- provided it's done right. The OCAML-based language F# accepts OCAML enclosing tokens, but if you mark the groups with indentation they're not necessary (but still legal). That seems to me to work pretty cleanly. -- Tim Rowe -- http://mail.python.org/mailman/listinfo/python-list
How to replace the two last digits from an xml file?
Hi,
I am trying to get a value from an xml file, increment it by 1,
replace by the new value and write another xml with the new value
inside.
I have found this code to get the line and it works but I have to do
everything manualy:
import re
lines = open("c:\\File1.xml").readlines()
for i in range(len(lines)):
if re.search('national.number', lines[i]):
lines[i] = lines[i].replace
('01aaa02','01aaa03')
open("File2.xml","w").writelines(lines)
The goal I am trying to reach is to create 30 different xml.
Could someone help me?
Thanks
Al
--
http://mail.python.org/mailman/listinfo/python-list
Re: where is the PyString_AsString in Python 3.0?
BigHand gmail.com> writes: > > There is no PyString_AsString. Everything >> string is unicode now. (PyUnicode API) > hello,Ben, > could you give me an example? I almost know the > PyUnicode API,but the > docs of 3.0 is too brief for me. PyString_FromString -> PyUnicode_FromString PyString_Concat -> PyUnicode_Concat etc... To get a char * you have to explicitly encode the string with PyUnicode_AsEncodedString. -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Emanuele D'Arrigo wrote: Hi everybody, while testing a module today I stumbled on something that I can work around but I don't quite understand. *Do NOT use "is" to compare immutable types.***Ever! ** It is an implementation choice (usually driven by efficiency considerations) to choose when two strings with the same value are stored in memory once or twice. In order for Python to recognize when a newly created string has the same value as an already existing string, and so use the already existing value, it would need to search *every* existing string whenever a new string is created. Clearly that's not going to be efficient. However, the C implementation of Python does a limited version of such a thing -- at least with strings of length 1. Gary Herron a = "a" b = "a" a == b True a is b True c = "/a" d = "/a" c == d True # all good so far c is d False # ek! Why c and d point to two different objects with an identical string content rather than the same object? Manu -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: "/a" is not "/a" ?
Emanuele D'Arrigo wrote: c = "/a" d = "/a" c == d > True # all good so far c is d > False # ek! > > Why c and d point to two different objects with an identical string > content rather than the same object? Because you instantiated two difference objects. http://docs.python.org/reference/datamodel.html#objects-values-and-types should get you started on Python and objects. j -- http://mail.python.org/mailman/listinfo/python-list
searching for an easy library to create OpenOffice spreadsheets
Hello all, I am looking out for a python library which does the followingg. 1, create and manipulate openoffice spreadsheets. 2, allow for cell formatting including merging cells. 3, allow for colouring cells and formatting data as bold italics etc. 4, alignment of data should be possible. I looked at ooolib but did not find a method for merging cells. any ideas? happy hacking. Krishnakant. -- http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao, the official 1.0 version is released
Limin Fu wrote: > To Tim Greer and others: > > Some people may think this kind of announcement are off topic in a > group for another language. This is not exactly true. This is still > about programming, there are so many programmers out there, who knows > if there would be somebody interested in a new language. This > announcement does not mean to threaten any language, I don't even > think it is somewhere close to that. So take it easy. I don't see it as a threat at all (I'm not sure how you read that from what I said), and I honestly don't care that much, but it seems pretty odd to post about a completely different language in groups that have no relation. Imagine people posting announcements about languages, modules, extensions, etc in other language groups as they happened, we'd see 1/2 the group's posts containing that sort of information. You posted in the Python, Perl and Ruby groups, and it just seemed (was) inappropriate and not a good way to get people interested (it can be a turn off to see what could be considered spam). Just because it's another language doesn't make it on topic. There are over a hundred of them out there, and even more derivatives and it's just not usually appreciated (though I don't pretend to speak for anyone else, but it's a pretty accurate observation). I don't assume ill intent by you, but it was questionable about why. Anyway, it's not a knock on the language, I just don't think the Perl, Ruby or Python groups are relevant (but maybe some people will find it interesting and be glad you did -- of course, that could be said of any post about anything). -- Tim Greer, CEO/Founder/CTO, BurlyHost.com, Inc. Shared Hosting, Reseller Hosting, Dedicated & Semi-Dedicated servers and Custom Hosting. 24/7 support, 30 day guarantee, secure servers. Industry's most experienced staff! -- Web Hosting With Muscle! -- http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao, the official 1.0 version is released
Honest to say, there is no solid connection between Dao and Python. It's just that I had received some good suggestions and comments from these groups when I made a few previous announcements in these groups. So I guessed somebody might be interested in Dao, and thought it might be a good idea to announce it here again. Nevertheless, Python is one of the few languages from which Dao tried to learn something. I have paid a lot of my attention to Python during the development of Dao. Once a time I even created a module trying to allow calling Python functions and using python objects in Dao scripts, it was a long time ago, probably even before this language is named as Dao. Unfortunately I hadn't time to continue to develop that module. To Tim Greer and others: Some people may think this kind of announcement are off topic in a group for another language. This is not exactly true. This is still about programming, there are so many programmers out there, who knows if there would be somebody interested in a new language. This announcement does not mean to threaten any language, I don't even think it is somewhere close to that. So take it easy. On 3月6日, 下午7时13分, s...@pobox.com wrote: > Limin> This is to announce the first official release of Dao. > > What's the connection to Python? > > -- > Skip Montanaro - s...@pobox.com -http://www.smontanaro.net/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Unusual Python interpreter problem with os.fork()
On Mar 6, 7:20 am, Jean-Paul Calderone wrote: > On Fri, 6 Mar 2009 05:00:03 -0800 (PST), DLitgo wrote: > >Hello everyone, > > >I have a curious problem which I'm wondering if anyone here can shed > >some light on. I'm basically just following along with a guide which > >is going through some of the os module, and I'm running some examples > >in the python interpreter on mac os x (accessed through terminal/ > >bash). > > >Basically all I did was use os.fork() which caused this strange > >problem: > > >Macintosh:~ $ python > >Python 2.5.1 (r251:54863, Jan 13 2009, 10:26:13) > >[GCC 4.0.1 (Apple Inc. build 5465)] on darwin > >Type "help", "copyright", "credits" or "license" for more information. > > import os > pid = os.fork() > > As soon as this returns, you have two CPython processes reading from stdin > and writing to stdout. They fight over your input and their output gets > interleaved in non-deterministic ways. Basically, you probably don't ever > want to do this. > > Jean-Paul Okay cool, I guess the example wasn't meant to be run in the interpreter then :) Thanks for the reply. -- http://mail.python.org/mailman/listinfo/python-list
Re: Reading from text
On Feb 17, 11:03 am, oamram wrote:
> Hi All,
> new to python. i have a directory with about 50 text file and i need to
> iterate through them and get
> line 7 to 11 from each file and write those lines into another file(one file
> that will contain all lines).
>
import glob
file("output.txt","w").write('\n'.join( "".join(f.readlines()
[7:11+1]) ) for f in glob.glob("targetdir/*.txt"))
-- Paul
--
http://mail.python.org/mailman/listinfo/python-list
Re: Asking for prophecy
3 and 2.6 are compatible. so develop on 3, to make sure you don't use old junk, and then switch to 2.6 if you need to. there are a few wrinkles in doing so, but it is not a big problem. 3.0 is a nicer language. it's cleaner and more consistent. i think important libraries will move there. no-one wants to do a perl. it's the likely future and you can always jump back to 2.6 if needed. and in the long term, we will all die. andrew Stefan Spoettl wrote: > In the pass it was always a good idea to use the newest Python verison for > starting the development of a new application. First one could benefit > from the additional features and second one could be sure that the > community would have been passing during development. > > Nowadays we have at least three Python versions (2.5, 2.6, 3.0) on our > machines and - damned! - I really don't know which version I should use > for my next development. The Unix-like systems as much as the major part > of well maintained third party libraries are remaining "penetrantly" on > 2.5. Why the vangard of the community don't like to use at least 2.6 for > bridging to the future Python? Is this the mutiny against the empery of > the BDFL or is the vangard just asking for some more time? If I want to > attest my personal attachment to the king by using 3.0, what will happen? > Will I be deserted someday? > > Stefan-- > http://mail.python.org/mailman/listinfo/python-list > -- http://mail.python.org/mailman/listinfo/python-list
"/a" is not "/a" ?
Hi everybody, while testing a module today I stumbled on something that I can work around but I don't quite understand. >>> a = "a" >>> b = "a" >>> a == b True >>> a is b True >>> c = "/a" >>> d = "/a" >>> c == d True # all good so far >>> c is d False # ek! Why c and d point to two different objects with an identical string content rather than the same object? Manu -- http://mail.python.org/mailman/listinfo/python-list
Re: how to prevent python import from looking into the current directory
(Could you please set a valid email address for people to contact you if necessary?) TP writes: > I would like to prevent the loading of modules in the current > directory. You will, I think, like the new distinction between “absolute” and “relative” imports http://www.python.org/dev/peps/pep-0328/>. -- \ “All my life I've had one dream: to achieve my many goals.” | `\—Homer, _The Simpsons_ | _o__) | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Asking for prophecy
In the pass it was always a good idea to use the newest Python verison for starting the development of a new application. First one could benefit from the additional features and second one could be sure that the community would have been passing during development. Nowadays we have at least three Python versions (2.5, 2.6, 3.0) on our machines and - damned! - I really don't know which version I should use for my next development. The Unix-like systems as much as the major part of well maintained third party libraries are remaining "penetrantly" on 2.5. Why the vangard of the community don't like to use at least 2.6 for bridging to the future Python? Is this the mutiny against the empery of the BDFL or is the vangard just asking for some more time? If I want to attest my personal attachment to the king by using 3.0, what will happen? Will I be deserted someday? Stefan-- http://mail.python.org/mailman/listinfo/python-list
Re: New User - Using tutorial and Docs - POST returns 302 Found
> Sorry, I think you didn't get my later post -- than in fact was from a
> month ago...
> Seehttp://article.gmane.org/gmane.comp.python.general/613312/
> urllib2 should handle a 302 redirect automatically.
>
> --
> Gabriel Genellina
I went to the link you provided and sure enough there was your post.
However, the date was all wrong. I did not even submit to this list
until March 2,2009 so the date on your other post was probably in
European format 03/02/2009 but read as US 02/03/2009. In any case,
thank you. The code does get my request to the page however the data
sent in the POST does not arrive with the request.
import httplib, urllib, urllib2
f = open(r'C:\Users\Owner\Desktop\mydata.txt', 'r')
read_data = f.read()
f.close()
params = urllib.urlencode({'textarea1': read_data})
headers = {"Content-type": "application/x-www-form-urlencoded",
"Accept": "text/plain"}
url = "http://www.thenational.us:80/pages/start/test/getpost.html";
req = urllib2.Request(url, params, headers)
response = urllib2.urlopen(req)
data = response.read()
response.close()
print data
f = open(r'C:\Users\Owner\Desktop\pydata.txt', 'a')
f.write(data)
f.close()
I even changed the params line to to:
params = urllib.urlencode({'textarea1': 'somedata'})
then I tried taking part of the header out ("Accept": "text/plain")
like this:
headers = {"Content-type": "application/x-www-form-urlencoded"}
I still get to the getpost.html page because response has the html
from that page, but textarea1 does not get passed.
Putting :80 or leaving it out of the URL does not seem to matter
either way I get to the getpost page, just no data is passed.
I am running Python 2.5 r25:51908 MSC v.1318 32 bit (Intel) on wind32
and after doing a search on Python Post problems, I read that urllib2
handled 302 redirect POST incorrectly at least in 2.5x . See
http://bugs.python.org/issue1401
Maybe my code is still lacking some command, or I need to install a
newer version of Python. That option (installing) seems a little
daunting to me as I have no experience but I can learn if that will
fix the problem for me.
Thanks for the help so far, any furhter suggestions appreciated.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Winsound Problems on Vista 64
Casey wrote: I have a new laptop that came with Vista 64 and I'm having problems with some of my older code that I use for multimedia processing. I narrowed the problem down to the winsound library; any attempt to play sounds results in a fatal error. The simplest case is: from winsound import Beep Beep(440, 2) Traceback (most recent call last): File "", line 1, in RuntimeError: Failed to beep I have been able to recreate this problem in Python 2.6.1 (32-bit), 3.0.1 (32-bit) and 3.0.1 (AMD64 bit, which I hope is compliant with my IA64 CPU). IA64 is Itanium, not Pentium, and AMD64 is not compatible with that. But I doubt that is what your laptop has. -- http://mail.python.org/mailman/listinfo/python-list
