Re: Can't do a multiline assignment!
On 17 avr, 18:19, [EMAIL PROTECTED] wrote: > On Apr 17, 10:54 am, [EMAIL PROTECTED] wrote: > > > On 17 avr, 17:40, [EMAIL PROTECTED] wrote: > > > Out of sheer curiosity, why do you need thirty (hand-specified and > > dutifully commented) names to the same constant object if you know > > there will always be only one object? > > I'm building a web server. The many variables are names of header > fields. One part of the code looks like this (or at least I'd like it > to): > > class RequestHeadersManager: > > # General header fields > Cache_Control = \ > Connection = \ > Date= \ > Pragma = \ > Trailer = \ > Transfer_Encoding = \ > Upgrade = \ > Via = \ > Warning = \ > > # Request header fields > Accept = \ > Accept_Charset = \ > Accept_Encoding = \ > Accept_Language = \ > Authorization = \ > ... > > Etc etc etc. At the end they'll all be assign to None. Then, when > initialized, __init__() will the the string of headers, parse them, > and use those variables shown above to assign to the header values. Of > course a normal request won't include all of those headers, so the > others will remain None. That's what I want. Ah, so they are not constant, I was mislead by the name 'CONSTANTn' in your OP. But why would you insist on: """ # helpful comment CONSTANT1 = \ # there too CONSTANT2 = \ CONSTANT3 = \ None """ rather than: """ # helpful comment CONSTANT1 = None # there too CONSTANT2 = None CONSTANT3 = None """ or even: """ CONSTANT = None # helpful comment CONSTANT1 = CONSTANT # there too CONSTANT2 = CONSTANT CONSTANT3 = CONSTANT """ (hopefully you don't consider those names in your code. ^ ^) -- http://mail.python.org/mailman/listinfo/python-list
Re: Can't do a multiline assignment!
On 17 avr, 17:40, [EMAIL PROTECTED] wrote: > > Yuck! No way!! If you *want* to make your code that hard to read, I'm > > sure you can find lots of ways to do so, even in Python, but don't > > expect Python to change to help you toward such a dubious goal. > > Well, my actual code doesn't look like that. Trust me, I like clean > code. > > > Seriously, examine your motivations for wanting such a syntax. Does it > > make the code more readable? (Absolutely not.) Does it make it more > > maintainable. (Certainly not -- consider it you needed to change > > CONSTANT2 to a different value some time in the future.) > > Yes, it makes it more readable. And yes, it does make it (a lot) more > maintainable. Mainly because I don't have those four variables, I have > about thirty. And I think I won't need to one or two of them, but > maybe all of them at once. Out of sheer curiosity, why do you need thirty (hand-specified and dutifully commented) names to the same constant object if you know there will always be only one object? -- http://mail.python.org/mailman/listinfo/python-list
Re: Python and stale file handles
On 17 avr, 14:43, [EMAIL PROTECTED] wrote:
> On 17 Apr, 04:22, tgiles <[EMAIL PROTECTED]> wrote:
>
>
>
> > Hi, All!
>
> > I started back programming Python again after a hiatus of several
> > years and run into a sticky problem that I can't seem to fix,
> > regardless of how hard I try- it it starts with tailing a log file.
>
> > Basically, I'm trying to tail a log file and send the contents
> > elsewhere in the script (here, I call it processor()). My first
> > iteration below works perfectly fine- as long as the log file itself
> > (logfile.log) keeps getting written to.
>
> > I have a shell script constantly writes to the logfile.log... If I
> > happen to kill it off and restart it (overwriting the log file with
> > more entries) then the python script will stop sending anything at all
> > out.
>
> > import time, os
>
> > def processor(message,address):
> > #do something clever here
>
> > #Set the filename and open the file
> > filename = 'logfile.log'
> > file = open(filename,'r')
>
> > #Find the size of the file and move to the end
> > st_results = os.stat(filename)
> > st_size = st_results[6]
> > file.seek(st_size)
>
> > while 1:
> > where = file.tell()
> > line = file.readline()
> > if not line:
> > time.sleep(1)
> > file.seek(where)
> > else:
> > print line, # already has newline
> > data = line
> > if not data:
> > break
> > else:
> > processor(data,addr)
> > print "Sending message '",data,"'."
>
> > someotherstuffhere()
>
> > ===
>
> > This is perfectly normal behavior since the same thing happens when I
> > do a tail -f on the log file. However, I was hoping to build in a bit
> > of cleverness in the python script- that it would note that there was
> > a change in the log file and could compensate for it.
>
> > So, I wrote up a new script that opens the file to begin with,
> > attempts to do a quick file measurement of the file (to see if it's
> > suddenly stuck) and then reopen the log file if there's something
> > dodgy going on.
>
> > However, it's not quite working the way that I really intended it to.
> > It will either start reading the file from the beginning (instead of
> > tailing from the end) or just sit there confuzzled until I kill it
> > off.
>
> > ===
>
> > import time, os
>
> > filename = logfile.log
>
> > def processor(message):
> > # do something clever here
>
> > def checkfile(filename):
> > file = open(filename,'r')
> > print "checking file, first pass"
> > pass1 = os.stat(filename)
> > pass1_size = pass1[6]
>
> > time.sleep(5)
>
> > print "file check, 2nd pass"
> > pass2 = os.stat(filename)
> > pass2_size = pass2[6]
> > if pass1_size == pass2_size:
> > print "reopening file"
> > file.close()
> > file = open(filename,'r')
> > else:
> > print "file is OK"
> > pass
>
> > while 1:
> > checkfile(filename)
> > where = file.tell()
> > line = file.readline()
> > print "reading file", where
> > if not line:
> > print "sleeping here"
> > time.sleep(5)
> > print "seeking file here"
> > file.seek(where)
> > else:
> > # print line, # already has newline
> > data = line
> > print "readying line"
> > if not data:
> > print "no data, breaking here"
> > break
> > else:
> > print "sending line"
> > processor(data)
>
> > So, have any thoughts on how to keep a Python script from bugging out
> > after a tailed file has been refreshed? I'd love to hear any thoughts
> > you my have on the matter, even if it's of the 'that's the way things
> > work' variety.
>
> > Cheers, and thanks in advance for any ideas on how to get around the
> > issue.
>
> > tom
>
> Possibly, restarting the program that writes the log file creates a
> new file rather than
> appending to the old one??
It seems at least the op should definitely reopen the file:
# create a file
In [322]: f1 = open("test.txt", 'w')
In [323]: f1.write("test\n")
In [324]: f1.close()
# check content of file
In [325]: f_test1 = open("test.txt")
In [326]: f_test1.readline()
Out[326]: 'test\n'
# check twice, we never know
In [327]: f_test1.seek(0)
In [328]: f_test1.readline()
Out[328]: 'test\n'
# rewrite over the same file
In [329]: f1 = open("test.txt", 'w')
In [330]: f1.write("new test\n")
In [331]: f1.close()
# check if ok
In [332]: f_test2 = open("test.txt")
In [333]: f_test2.readline()
Out[333]: 'new test\n'
# first file object has not seen the change
In [334]: f_test1.seek(0)
In [335]: f_test1.readline()
Out[335]: 'test\n'
--
http://mail.python.org/mailman/listinfo/python-list
Re: def power, problem when raising power to decimals
On 17 avr, 00:49, "Gabriel Genellina" <[EMAIL PROTECTED]> wrote: > En Wed, 16 Apr 2008 19:21:18 -0300, John Machin <[EMAIL PROTECTED]> > escribió: > > > [EMAIL PROTECTED] wrote: > >> also i found a link which states 0^0 isnt 1 even though every > >> calculator ive tried says it is. > >> it doesnt say what it is but i presume 0 then. > >> but it seems the dude is wrong and it is 1? > > > Of the possible results of 0 ** 0 (i.e. 1, 0, and NaN), 1 seems to be > > the least implausible. It allows X ** 0 to be 1 for all X. > > But a result of 0 would allow 0 ** X to be 0 for all X. (btw, this is the > reason lim(x**x) for x->0 does not exist) lim(x**x) for x->0+ is well defined, exists and equals 1. [1] As x**x is continuous in 0+, it is widely customary to have: 0**0:=1 [1] Recall that x**x := exp(x*log(x)) The limit of x*log(x) for x->0 is 0 [2] therefore lim(x**x) for x->0 is 1. [2] Let y = 1/x; x*log(x)= -log(y)/y and the limit of log(y)/y for y-> +inf is 0. -- http://mail.python.org/mailman/listinfo/python-list
Re: vary number of loops
On 16 avr, 15:31, [EMAIL PROTECTED] wrote: > Hi everyone, > > I'm new to Python and the notion of lambda, and I'm trying to write a > function that would have a varying number of nested for loops > depending on parameter n. This just smells like a job for lambda for > me, but I can't figure out how to do it. Any hint? > > For example, for n=2, I want the function to look something like: > > def foo(2) >generate 2 sets of elements A, B ># mix elements by: >for a_elt in A > for b_elt in B > form all combinations of them > > If n=3, I want to have 3 sets of elements and mix them up using 3 for > loops. > > Any help is greatly appreciated, > > nullgraph You can try recursion in a more classic manner: In [283]: def foo(n): .: def bar(n): .: my_elts = xrange(2) .: if n<=0: .: raise StopIteration .: elif n<=1: .: for elt in my_elts: .: yield (elt,) .: else: .: for elt in my_elts: .: for o_elt in bar(n-1): .: yield (elt,)+o_elt .: for elt in bar(n): .: print elt .: In [284]: foo(2) (0, 0) (0, 1) (1, 0) (1, 1) In [285]: foo(3) (0, 0, 0) (0, 0, 1) (0, 1, 0) (0, 1, 1) (1, 0, 0) (1, 0, 1) (1, 1, 0) (1, 1, 1) In this case, I have an inner function to generate the whole set of elements and then an outer loop to process them. Note that you can have the generation of my_elts depend on rank n of recursion (that is the index of the set in your list). -- http://mail.python.org/mailman/listinfo/python-list
Re: insert python script in current script
On 16 avr, 09:42, "Prashant" <[EMAIL PROTECTED]> wrote:
> I was wondering is there any way to do this:
>
> I have written a class in python and __init__ goes like this:
>
> def __init__(self):
>
> self.name = 'jack'
> self.age = 50
>
> import data
>
> now here there is data.py in the same directory and contents are like:
>
> self.address = 'your address'
> self.status = 'single'
>
> The problem is 'self' is giving some error here. I need to know if
> somehow I can do this. It's like inserting the script as it's part of
> the file itself.
The purpose of import is to build a module object, which implies
executing the module file but in a new context.
If you simply want to execute some code in a file, you can try
execfile("filename"):
In [243]: class A(object):
.: def __init__(self):
.: execfile("test.py")
.:
In [244]: a=A()
In [245]: a.a
Out[245]: 1
In [246]: open("test.py").read()
Out[246]: 'self.a = 1\n'
But do you really want to execute some arbitrary code or to initialize
values with some kind of configuration file?
>
> Cheers
--
http://mail.python.org/mailman/listinfo/python-list
Re: use object method without initializing object
On 15 avr, 17:43, Robert Bossy <[EMAIL PROTECTED]> wrote: > Reckoner wrote: > > would it be possible to use one of an object's methods without > > initializing the object? > > > In other words, if I have: > > > class Test: > > def __init__(self): > > print 'init' > > def foo(self): > > print 'foo' > > > and I want to use the foo function without hitting the > > initialize constructor function. > > > Is this possible? > > Hi, > > Yes. It is possible and it is called "class method". That is to say, it > is a method bound to the class, and not to the class instances. > In pragmatic terms, class methods have three differences from instance > methods: >1) You have to declare a classmethod as a classmethod with the > classmethod() function, or the @classmethod decorator. >2) The first argument is not the instance but the class: to mark this > clearly, it is usually named cls, instead of self. >3) Classmethods are called with class objects, which looks like this: > ClassName.class_method_name(...). > > In your example, this becomes: > > class Test(object): > def __init__(self): > print 'init' > @classmethod > def foo(cls): > print 'foo' > > Now call foo without instantiating a Test: > Test.foo() To be complete, you can also define a static method that will not even be passed the class as argument: In [217]: class Test(object): .: def __init__(self): .: print 'init' .: @staticmethod .: def foo(): .: print 'foo' .: In [218]: Test.foo() foo -- http://mail.python.org/mailman/listinfo/python-list
Re: use object method without initializing object
On 15 avr, 17:27, Reckoner <[EMAIL PROTECTED]> wrote: > would it be possible to use one of an object's methods without > initializing the object? > > In other words, if I have: > > class Test: > def __init__(self): > print 'init' > def foo(self): > print 'foo' > > and I want to use the foo function without hitting the > initialize constructor function. > > Is this possible? Yes: In [214]: class Test: .: def foo(self): .: print 'foo' .: In [215]: t = Test() In [216]: t.foo() foo -- http://mail.python.org/mailman/listinfo/python-list
Re: Rounding a number to nearest even
On 14 avr, 20:02, Thomas Dybdahl Ahle <[EMAIL PROTECTED]> wrote: > On Fri, 2008-04-11 at 03:14 -0700, bdsatish wrote: > > The built-in function round( ) will always "round up", that is 1.5 is > > rounded to 2.0 and 2.5 is rounded to 3.0. > > > If I want to round to the nearest even, that is > > > my_round(1.5) = 2# As expected > > my_round(2.5) = 2# Not 3, which is an odd num > > > I'm interested in rounding numbers of the form "x.5" depending upon > > whether x is odd or even. Any idea about how to implement it ? > > This seams to work fine: > evenRound = lambda f: round(f/2.)*2 That was the solution I proposed first but it is inadequate since the op does not want 3 to be rounded to 4. If you're interested in this discussion, I kindly suggest you read the whole thread: many interesting proposals and discussions have ensued. -- http://mail.python.org/mailman/listinfo/python-list
Re: eval modifies passed dict
On 14 avr, 18:05, Duncan Booth <[EMAIL PROTECTED]> wrote:
> Janto Dreijer <[EMAIL PROTECTED]> wrote:
> > It seems eval is modifying the passed in locals/globals. This is
> > behaviour I did not expect and is really messing up my web.py app.
>
> > Python 2.5.1 (r251:54863, Mar 7 2008, 04:10:12)
> > [GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2
> > Type "help", "copyright", "credits" or "license" for more information.
> d = dict(a=1)
> d.keys()
> > ['a']
> eval("a", d)
> > 1
> d.keys()
> > ['a', '__builtins__']
>
> > That can't be right.
>
> That can exactly be right.
>
> The current document is (I think) wrong or at the least misleading. It
> says:
>
> > If the globals dictionary is present and lacks '__builtins__', the
> > current globals are copied into globals before expression is parsed.
>
> I think it should say:
>
> > If the globals dictionary is present and lacks '__builtins__', the
> > current value of __builtins__ is added to globals before expression
> > is parsed.
>
> i.e. only a single variable is assigned, other globals aren't copied.
Indeed:
Python 2.5.1 (r251:54863, Mar 7 2008, 03:39:23)
[GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> globals().keys()
['__builtins__', '__name__', '__doc__']
>>> b = 2
>>> d = {'a': 1}
>>> eval('a', d)
1
>>> d.keys()
['a', '__builtins__']
--
http://mail.python.org/mailman/listinfo/python-list
Re: eval modifies passed dict
On 14 avr, 17:23, Janto Dreijer <[EMAIL PROTECTED]> wrote:
> It seems eval is modifying the passed in locals/globals. This is
> behaviour I did not expect and is really messing up my web.py app.
>
> Python 2.5.1 (r251:54863, Mar 7 2008, 04:10:12)
> [GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.>>> d =
> dict(a=1)
> >>> d.keys()
> ['a']
> >>> eval("a", d)
> 1
> >>> d.keys()
>
> ['a', '__builtins__']
>
> That can't be right.
>From the documentation of eval[1]
"If the globals dictionary is present and lacks '__builtins__', the
current globals are copied into globals before expression is parsed."
[1]http://docs.python.org/lib/built-in-funcs.html
--
http://mail.python.org/mailman/listinfo/python-list
Re: Rounding a number to nearest even
On 11 avr, 14:14, Gerard Flanagan <[EMAIL PROTECTED]> wrote: > On Apr 11, 2:05 pm, Gerard Flanagan <[EMAIL PROTECTED]> wrote: > > > On Apr 11, 12:14 pm, bdsatish <[EMAIL PROTECTED]> wrote: > > > > The built-in function round( ) will always "round up", that is 1.5 is > > > rounded to 2.0 and 2.5 is rounded to 3.0. > > > > If I want to round to the nearest even, that is > > > > my_round(1.5) = 2# As expected > > > my_round(2.5) = 2# Not 3, which is an odd num > > > > I'm interested in rounding numbers of the form "x.5" depending upon > > > whether x is odd or even. Any idea about how to implement it ? > In fact you can avoid the call to the builtin round: Alternatively, you can avoid the test using both divmod and round: In [55]: def myround(x): .: d, m = divmod(x, 2) .: return 2*d + 1 + round(m-1) .: In [58]: assert myround(3.2) == 3 In [59]: assert myround(3.6) == 4 In [60]: assert myround(3.5) == 4 In [61]: assert myround(2.5) == 2 In [62]: assert myround(-0.5) == 0.0 In [63]: assert myround(-1.5) == -2.0 In [64]: assert myround(-1.3) == -1.0 In [65]: assert myround(-1.8) == -2 In [66]: assert myround(-2.5) == -2.0 -- http://mail.python.org/mailman/listinfo/python-list
Re: Rounding a number to nearest even
On 11 avr, 12:14, bdsatish <[EMAIL PROTECTED]> wrote: > The built-in function round( ) will always "round up", that is 1.5 is > rounded to 2.0 and 2.5 is rounded to 3.0. > > If I want to round to the nearest even, that is > > my_round(1.5) = 2# As expected > my_round(2.5) = 2# Not 3, which is an odd num > > I'm interested in rounding numbers of the form "x.5" depending upon > whether x is odd or even. Any idea about how to implement it ? When you say "round to the nearest even", you mean new_round(3) <> 3? Is so, you can try: In [37]: def new_round(x): : return round(x/2.)*2 : In [38]: new_round(1.5) Out[38]: 2.0 In [39]: new_round(2.5) Out[39]: 2.0 In [40]: new_round(3) Out[40]: 4.0 -- http://mail.python.org/mailman/listinfo/python-list
