Re: XP rich text cut-n-paste
Paddy: Scintilla does indeed have the feature, and googling for the term copy as RTF lead me to http://www.pnotepad.org/ which also has the feature. Its actually implemented in SciTE rather than Scintilla by the ugly technique of writing out an RTF file and then copying that to the clipboard. It only works on Windows due to the simpler clipboard API compared to X and since RTF is a common format on Windows. Other projects sometimes include code from SciTE even though the code isn't really written for reuse. Neil -- http://mail.python.org/mailman/listinfo/python-list
raw strings and \
I thought I understood raw strings, then I got bitten by this: x=r'c:\blah\' which is illegal! I thought that \ had no special meanning in a raw string so why can't it be the last character? making me do: x=r'c:\blah' '\\' is just silly... -- http://mail.python.org/mailman/listinfo/python-list
django and mod_python
Hi, I read the mod_python documentation on the Django site but I'm getting this error: EnvironmentError: Could not import DJANGO_SETTINGS_MODULE 'accesshiphop.settings' (is it on sys.path?): No module named accesshiphop.settings Here's my httpd.conf: Location /public_html/myproject/ PythonPath [r'c:/apache/public_html/myproject/']+sys.path SetHandler python-program PythonHandler django.core.handlers.modpython SetEnv DJANGO_SETTINGS_MODULE myproject.settings PythonDebug On /Location Also, the Django site says Also, if you've manually altered your PYTHONPATH to put your Django project on it, you'll need to tell mod_python: I don't recall adding my project to my PYTHONPATH. Should I have done this? How do I do this? Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: raw strings and \
wrote: I thought I understood raw strings, then I got bitten by this: x=r'c:\blah\' which is illegal! I thought that \ had no special meanning in a raw string so why can't it be the last character? No, the backslash is still special in terms of parsing the string, it is simply that once the string has been parsed escape sequences are not interpreted. making me do: x=r'c:\blah' '\\' is just silly... Yes, that is silly. You could alternatively do: x = 'c:/blah/' or x = 'c:\\blah\\' But why would you want to end your path with a literal backslash anyway? Get into the habit of using the os.path module for all manipulations of file paths and you never need to worry about this sort of thing again. This sort of thing should work well enough: folder = 'c:/blah' for line in open(os.path.join(folder, 'data.txt')): print line -- http://mail.python.org/mailman/listinfo/python-list
Re: XP rich text cut-n-paste
Paddy wrote: Is their a colourized editor/shell that allows you to cut and paste the colourized text? Idle, SPE, Eclipse, and pythonwin all seem to nicely colourize both command line input as well as editor windows but when I cut and paste (in this case, into OpenOffice Writer), even the paste-special menu just allows the pasting of un-adorned text. i have a work-around: gvim coourizes and allows export as html, but it is long-winded. Epsilon (www.lugaru.com) has a 'copy-formatting-as-html' command (new in the version currently in beta). Unfortunately is isn't a free editor (although you can download a time limited beta of the next version for free if you want to try it out). -- http://mail.python.org/mailman/listinfo/python-list
is there such a built-in funciton, similar to filter
Hello, Beginner learning Python here. I know filter(lambda x: x 3, [1, 2, 5, -3, 4, 8]) will give me a list [5, 4, 8]. What if I only need to find the first item in the list that returns Ture when applying the filter function. In this case, I only want to get the 5, and its index 2. Is there a built-in function, or function from a module for that? I think it is not hard to write a function for this. But knowing Python is battery included, I thought I'd like to ask. Thanks for your help. - wcc -- http://mail.python.org/mailman/listinfo/python-list
Re: django and mod_python
[EMAIL PROTECTED] wrote: Hi, I read the mod_python documentation on the Django site but I'm getting this error: EnvironmentError: Could not import DJANGO_SETTINGS_MODULE 'accesshiphop.settings' (is it on sys.path?): No module named accesshiphop.settings Here's my httpd.conf: Location /public_html/myproject/ PythonPath [r'c:/apache/public_html/myproject/']+sys.path SetHandler python-program PythonHandler django.core.handlers.modpython SetEnv DJANGO_SETTINGS_MODULE myproject.settings PythonDebug On /Location Also, the Django site says Also, if you've manually altered your PYTHONPATH to put your Django project on it, you'll need to tell mod_python: . in my setup the PythonPath statement puts the folder containing myproject onto the PythonPath in your case that might be PythonPath [r'c:/apache/public_html']+sys.path also I place the SetEnv DJANGO_SETTINGS_MODULE . before specifying the PythonHandler, but I am unsure if that is required (I guess it depends on exactly how apache sets up the location), but it's what I would do in a batch file for example. -- http://mail.python.org/mailman/listinfo/python-list
Re: is there such a built-in funciton, similar to filter
wcc wrote: Beginner learning Python here. I know filter(lambda x: x 3, [1, 2, 5, -3, 4, 8]) will give me a list [5, 4, 8]. What if I only need to find the first item in the list that returns Ture when applying the filter function. In this case, I only want to get the 5, and its index 2. Is there a built-in function, or function from a module for that? I think it is not hard to write a function for this. But knowing Python is battery included, I thought I'd like to ask. Thanks for your help. You can use a generator expression like this: items = [1, 2, 5, -3, 4, 8] ((index, item) for index, item in enumerate(items) if item 3).next() (2, 5) -- Michael Hoffman -- http://mail.python.org/mailman/listinfo/python-list
Re: Passing a method indirectly
Thanks - that worked! Thanks to the other replies also. -- http://mail.python.org/mailman/listinfo/python-list
lists: += vs. .append() oddness with scope of variables
I'd like to understand why += operator raises an error while .append() does not. My wild guess is the parses treats them differently but I cannot understand why this depends on scope of the variables (global or class variables): a = [0] class foo(object): def __init__(self): print a: , a # += does not work if 'a' is global #a += [1] a.append(2) print a= , a class bar(object): b = [0] def __init__(self): print b: , self.b # += *does* work if 'a' is class var self.b += [1] self.b.append(2) print b= , self.b if __name__ == '__main__': x = foo() y = bar() a: [0] a= [0, 2] b: [0] b= [0, 1, 2] uncommenting 'a += [1]' would raise: a: Traceback (most recent call last): File c1.py, line 26, in ? x = foo() File c1.py, line 7, in __init__ print a: , a UnboundLocalError: local variable 'a' referenced before assignment TIA sandro *:-) -- Sandro Dentella *:-) e-mail: [EMAIL PROTECTED] http://www.tksql.orgTkSQL Home page - My GPL work -- http://mail.python.org/mailman/listinfo/python-list
Re: lists: += vs. .append() oddness with scope of variables
Em Dom, 2006-03-05 às 11:49 +, Sandro Dentella escreveu: class foo(object): def __init__(self): print a: , a # += does not work if 'a' is global #a += [1] a.append(2) print a= , a Try with: a = [0] class foo(object): def __init__(self): global a print a: , a a += [1] a.append(2) print a= , a foo() -- Quem excele em empregar a força militar subjulga os exércitos dos outros povos sem travar batalha, toma cidades fortificadas dos outros povos sem as atacar e destrói os estados dos outros povos sem lutas prolongadas. Deve lutar sob o Céu com o propósito primordial da 'preservação'. Desse modo suas armas não se embotarão, e os ganhos poderão ser preservados. Essa é a estratégia para planejar ofensivas. -- Sun Tzu, em A arte da guerra -- http://mail.python.org/mailman/listinfo/python-list
Re: lists: += vs. .append() oddness with scope of variables
Sandro Dentella wrote: I'd like to understand why += operator raises an error while .append() does not. My wild guess is the parses treats them differently but I cannot understand why this depends on scope of the variables (global or class variables): a = [0] class foo(object): def __init__(self): print a: , a # += does not work if 'a' is global #a += [1] a.append(2) print a= , a Any assignment to a variable within a function means that the name to which you are assigning is regarded as a local variable (unless you use the 'global' statement to override that). += is a form of assignment, calling the append method is not an assignment. The solution here is simply to use 'global a' to tell the compiler that you meant to assign the the global variable rather than creating a new local variable. -- http://mail.python.org/mailman/listinfo/python-list
Re: Random Prime Generator/Modular Arithmetic
thanks for the webpage info, however theres a small error I found when trying to generate a prime number with more than 300 decimal digits. It comes up with File prime.py, line 84, in mod_square_pow return x*mod_square_pow(((a**2)%n),t,n,p*2) File prime.py, line 84, in mod_square_pow return x*mod_square_pow(((a**2)%n),t,n,p*2) File prime.py, line 73, in mod_square_pow if(p*2t): RuntimeError: maximum recursion depth exceeded in cmp Have you considered this? otherwise the algorithm is rather quick for generating large random prime numbers. Thanks for your help Tuvas wrote: Okay, I don't know if your farmiliar with the miller-rabin primality test, but it's what's called a probabalistic test. Meaning that trying it out once can give fake results. For instance, if you use the number 31 to test if 561 is prime, you will see the results say that it isn't. Mathematically, the most possible wrong answers is 1/4th of the numbers. Thus, one should try at least 10 times (A very standard value) in order to ensure that the number is not a psuedoprime, but indeed a real prime number. That was the intent of the loop of 10 without using the number. If this test fails, it will chose another random number to test. I could easily test with several small numbers, at least primes up to 20 would greatly reduce the number of miller-rabin tests to perform, and would speed up the process considerably. Might as well toss it in. Thanks for the tip on the urandom. I knew there had to be a better random number generator somewhere. I saw lots of stuff for os specific, but I'm trying to develop this as os independent. -- http://mail.python.org/mailman/listinfo/python-list
disabling the line buffer somehow
Hi, I'm trying to proxy all keys typed by the user to a process spawned via popen2. Unfortunately, I figured out that I can't control really interactive applications such as mc or aptitude. All user input seems to be line buffered. http://pexpect.sourceforge.net/ has some words about the situation: Q: Why not just use a pipe (popen())? So, I understand that I cannot write a simple python code to transperantly proxy everything between any process and user typing from stdin without handling the raw terminal. Would it work if I read from the controlling tty of the python interpreter and write to the controlling tty of spawned process byte by byte (or /dev/stdin /dev/stdout) Thanks.. -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload sqrt in a module?
Michael McNeil Forbes wrote: Is there anything really bad about the following? It works exactly as I would like, but I don't want to get in trouble down the road: module_f import math as my_math def set_math(custom_math): globals()['my_math'] = custom_math This seems clearer to me: def set_math(custom_math): global my_math my_math = custom_math Or, if one wants to use the from __ import * form: from math import * def set_math(custom_math): globals().update(custom_math.__dict__) This will cause interesting trouble if custom_math doesn't implement all the functions you use from math. Kent -- http://mail.python.org/mailman/listinfo/python-list
Argument Precedence (possible bug?)
Hello all,
I am just learning Python and have come across something I feel might
be a bug. Please enlightenment me... The following code presents a
challenge. How in the world do you provide an argument for *arg4?
##
def argPrecedence(par1, par2=0, par3=0, *par4, **par5):
print 'par1 =', par1, ' # positional argument'
print 'par2 =', par2, ' # keyword argument'
print 'par3 =', par3, ' # keyword argument'
print 'par4 =', par4, ' # argument converted to tuple'
print 'par5 =', par5, ' # argument converted to dictionary'
argPrecedence('arg1', arg3='arg3', arg2='arg2', arg5='arg5')
# argPrecedence Results:
par1 = arg1 # positional argument
par2 = arg2 # keyword argument
par3 = arg3 # keyword argument
par4 = () # argument converted to tuple
par5 = {'arg5': 'arg5'} # argument converted to dictionary
##
The code above is verbose with comments because I am just learning
Python and am creating my own examples and reference materials... Can
you solve the problem? If so, can you share the solution? If not, is
this a bug, limitation or is it a feature?
Thank you for your time on this one!
PS. I could be far off with this codes purpose; to try and create an
example that will house all the different possible parameters
(positional, keyword, * and **) in one single def statement.
--
Best Regards
Victor B. Gonzalez
--
http://mail.python.org/mailman/listinfo/python-list
Argument Precedence (possible bug?)
Hello all,
I am just learning Python and have come across something I feel might
be a bug. Please enlightenment me... The following code presents a
challenge. How in the world do you provide an argument for *arg4?
##
def argPrecedence(par1, par2=0, par3=0, *par4, **par5):
print 'par1 =', par1, ' # positional argument'
print 'par2 =', par2, ' # keyword argument'
print 'par3 =', par3, ' # keyword argument'
print 'par4 =', par4, ' # argument converted to tuple'
print 'par5 =', par5, ' # argument converted to dictionary'
argPrecedence('arg1', par3='arg3', par2='arg2', par5='arg5')
# argPrecedence Results:
par1 = arg1 # positional argument
par2 = arg2 # keyword argument
par3 = arg3 # keyword argument
par4 = () # argument converted to tuple
par5 = {'arg5': 'arg5'} # argument converted to dictionary
##
The code above is verbose with comments because I am just learning
Python and am creating my own examples and reference materials... Can
you solve the problem? If so, can you share the solution? If not, is
this a bug, limitation or is it a feature?
Thank you for your time on this one!
PS. I could be far off with this codes purpose; to try and create an
example that will house all the different possible parameters
(positional, keyword, * and **) in one single def statement.
--
Best Regards
Victor B. Gonzalez
--
http://mail.python.org/mailman/listinfo/python-list
Re: Argument Precedence (possible bug?)
Please forgive my call()
Change this:
argPrecedence('arg1', arg3='arg3', arg2='arg2', arg5='arg5')
to this:
argPrecedence('arg1', par3='arg3', par2='arg2', arg5='arg5')
Thanks!
--
http://mail.python.org/mailman/listinfo/python-list
Re: Argument Precedence (possible bug?)
Hello all,
I am just learning Python and have come across something I feel might
be a bug. Please enlightenment me... The following code presents a
challenge. How in the world do you provide an argument for *arg4?
##
def argPrecedence(par1, par2=0, par3=0, *par4, **par5):
print 'par1 =', par1, ' # positional argument'
print 'par2 =', par2, ' # keyword argument'
print 'par3 =', par3, ' # keyword argument'
print 'par4 =', par4, ' # argument converted to tuple'
print 'par5 =', par5, ' # argument converted to dictionary'
argPrecedence('arg1', par3='arg3', par2='arg2', arg5='arg5')
# argPrecedence Results:
par1 = arg1 # positional argument
par2 = arg2 # keyword argument
par3 = arg3 # keyword argument
par4 = () # argument converted to tuple
par5 = {'arg5': 'arg5'} # argument converted to dictionary
##
The code above is verbose with comments because I am just learning
Python and am creating my own examples and reference materials... Can
you solve the problem? If so, can you share the solution? If not, is
this a bug, limitation or is it a feature?
Thank you for your time on this one!
PS. I could be far off with this codes purpose; to try and create an
example that will house all the different possible parameters
(positional, keyword, * and **) in one single def statement.
--
Best Regards
Victor B. Gonzalez
--
http://mail.python.org/mailman/listinfo/python-list
Re: Argument Precedence (possible bug?)
vbgunz wrote:
I am just learning Python and have come across something I feel might
be a bug. Please enlightenment me... The following code presents a
challenge. How in the world do you provide an argument for *arg4?
##
def argPrecedence(par1, par2=0, par3=0, *par4, **par5):
print 'par1 =', par1, ' # positional argument'
print 'par2 =', par2, ' # keyword argument'
print 'par3 =', par3, ' # keyword argument'
print 'par4 =', par4, ' # argument converted to tuple'
print 'par5 =', par5, ' # argument converted to dictionary'
argPrecedence('arg1', arg3='arg3', arg2='arg2', arg5='arg5')
# argPrecedence Results:
par1 = arg1 # positional argument
par2 = arg2 # keyword argument
par3 = arg3 # keyword argument
par4 = () # argument converted to tuple
par5 = {'arg5': 'arg5'} # argument converted to dictionary
##
The code above is verbose with comments because I am just learning
Python and am creating my own examples and reference materials... Can
you solve the problem? If so, can you share the solution? If not, is
this a bug, limitation or is it a feature?
not sure what you think the bug is, but I suspect that you've completely
missed the point of what * and ** do, and how they're used in real code.
/F
--
http://mail.python.org/mailman/listinfo/python-list
Question re client/server and blocking
Hi all I am developing a multi-user business/accounting application. It is coming along nicely :-), though rather slowly :-( I have hit an issue which will require a lot of changes to the code I have written so far, together with an increase in complexity and all the bad things that follow from that. Before I go ahead and make the changes, I thought I would bounce it off the group and see if there is a simpler approach. It is a bit tricky to explain (yes I have read the Zen of Python) but here goes. There is a server component and a client component. All the business logic is performed on the server. The client communicates with the server via a socket. The server is multi-threaded - one thread per connection. The server receives messages from the client, and responds as quickly as possible. Sometimes it must respond by asking the client a question. It must not block while waiting for an answer, so this is how I handle it (pseudo code) - def handleMessage(self): mainloop.askQuestion(questionText,self.answerYes,self.answerNo) def answerYes(self): handle Yes answer def answerNo(self): handle No answer The main loop stores the function references, and sends the question to the client. When it gets a reply, it calls the appropriate function. It works well. The server performs field-by-field validation - it does not wait for the entire form to be submitted, but validates the data as soon as it has been entered. Depending on the context, the validation may have to pass a number of checks, which may pass through a number of layers, eventually returning True or False. e.g. - def validate(self,data): if not check1: return False if not check2: return False if not self.check3(data): return False if not self.check4(data): return False if not check5: return False return True check3(self,data): if not check3a: return False return True check4(self,data): if not check4a: return False if not self.check4b(data): return False return True Effectively the entire chain blocks until a result is returned, but provided each element performs its check quickly, this will not be noticeable. Now I have decided that, in some circumstances, I want the server to ask the client a question before returning True or False - it could be as simple as Are you sure?. This throws a large spanner into the above scheme. Each caller cannot be sure whether the callee (?) will return quickly or not, so it cannot afford to wait for a reply, otherwise it may block. The only solution I can think of looks like this - def validate(self,data,checkOk,checkNotOk): # checkOk and checkNotOk are functions passed by the caller self.data = data self.checkOk = checkOk self.checkNotOk = checkNotOk if not check1: self.checkNotOk() if not check2: self.checkNotOk() self.check3(self.data,self.check3Ok,self.checkNotOk) def check3Ok(self): self.check4(self.data,self.check4Ok,self.checkNotOk) def check4Ok(self): if not check5: checkNotOk() self.checkOk() The callee must then look like this - def check3(self,data,checkOk,checkNotOk): if check ok: checkOk() else: checkNotOk() Then on the odd occasion that the callee needs to ask a question, it can do this - def check4(self,data,checkOk,checkNotOk): mainloop.askQuestion(questionText,checkOk,checkNotOk) This is similar to Twisted's approach of deferreds and callbacks. However, I do not think that using Twisted would simplify any of this - I would still have to split my logic chain up into multiple callback functions. I believe that I can get this to work, that it will add a powerful layer of functionality to my app, and that I could eventually refactor it enough so that it is actually understandable. On the other hand, it is much more complex than what I have got at present, and to change my entire app to use this mechanism will be quite a task. Have I explained myself adequately? Has anyone come across a similar situation before? Any advice will be much appreciated. Thanks Frank Millman -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload sqrt in a module?
On Sat, 04 Mar 2006 23:07:12 -0800, Michael McNeil Forbes wrote: On Fri, 3 Mar 2006, Steven D'Aprano wrote: ... you can do this: import my_module my_module.set_environment(math) # or cmath, or numeric, or whatever Your my_module will be like this: # Warning: untested code. ENVIRON = None # global variables sometimes have their uses def f(x): if ENVIRON is None: raise ValueError(Uninitialised module!) # or use a custom exception return ENVIRON.sqrt(x) def set_environment(name): global ENVIRON ENVIRON = __import__(name) Does this help? Yes. However, this raises a question: Is this any different than directly modifying the globals, or is it just syntactic sugar. The keyword global instructs Python to make all references to the following name come from the global namespace. It is the correct way to do it (but not necessarily the *only* correct way, or *always* the correct way). In something as tiny as your example: def set_environment(name): globals()['ENVIRON'] = __import__(name) it may not make any practical difference which method you use. But in larger, more complex code, you are creating a rod for your own back. Try running these three functions, and explain the difference in their behaviour. def f1(): global parrot parrot = 3 parrot += 1 print parrot is %d % parrot def f2(): globals()[parrot] = 3 globals()[parrot] += 1 print parrot is %d % parrot def f3(): globals()[parrot] = 3 parrot += 1 print parrot is %d % parrot Directly modifying the globals is playing around with Python's internals. You are allowed to do that, and sometimes it is the right thing to do, otherwise Guido wouldn't have made globals() writable. E.g. you have code where you want -- heaven knows why -- a name to refer to both a local and a global variable. This will work: def func(): x = 5 # x is local globals()['x'] = 3 # but this x is global I don't know whether writing to globals() is guaranteed to work for all variants of Python (CPython, Jython, PyPy, IronPython ... ) or if it is likely to change in Python 3. But even if modifying globals() is officially allowed, it still has a whiff of the sort of code-smell that Joel Spolsky talks about: http://www.joelonsoftware.com/articles/Wrong.html In my opinion, manipulating globals() is one of those things that ring warning bells in my head. It might not be *wrong*, exactly, but I'll want to pay extra attention to any function that does that. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: is there such a built-in funciton, similar to filter
Thanks a lot Michael. -- http://mail.python.org/mailman/listinfo/python-list
Re: Argument Precedence (possible bug?)
vbgunz wrote: I am just learning Python and have come across something I feel might be a bug. Please enlightenment me... The following code presents a challenge. How in the world do you provide an argument for *arg4? Maybe by putting that in the list of arguments? ... You don't even *have* an arg4 in the list, so how are we supposed to know what you are asking without guessing? Please consider rephrasing the question. -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: Python advocacy in scientific computation
Robert Kern wrote: That said, we have an excellent array object far superior to Matlab's. http://numeric.scipy.org/ I'd like to ask, being new to python, in which ways is this array object far superior to Matlab's? (I'm not being sarcastic, I really would like to know!) I've heard similar things about matplotlib, about how it surpasses Matlab's graphics. I haven't personally experienced this, but I'd like to know in which ways it is. bb -- - [EMAIL PROTECTED] http://web.bryant.edu/~bblais -- http://mail.python.org/mailman/listinfo/python-list
Re: Argument Precedence (possible bug?)
On Sun, 05 Mar 2006 04:45:05 -0800, vbgunz wrote: Hello all, I am just learning Python and have come across something I feel might be a bug. Please enlightenment me... The following code presents a challenge. How in the world do you provide an argument for *arg4? ## def argPrecedence(par1, par2=0, par3=0, *par4, **par5): print 'par1 =', par1, ' # positional argument' print 'par2 =', par2, ' # keyword argument' print 'par3 =', par3, ' # keyword argument' print 'par4 =', par4, ' # argument converted to tuple' print 'par5 =', par5, ' # argument converted to dictionary' No, you are confused about * and ** arguments. They don't convert arguments, they collect them. def f(a, b=0, *args, **kwargs): print a =, a print b =, b print args =, args print kwargs =, kwargs Now call the function different ways, and see which will work and which won't. f(1) f(1, 2) f(1, b=2) f(a=1, b=2) f(b=2, a=1) Notice that this does not work: f(b=3) Do you understand why not? Now look at these calls: f(1, 2, 3) f(1, 2, 3, 4, 5, 6) f(1, 2, 3, 4, 5, 6, foo=7, bar=8) In the function definition f(a, b=0, *args, **kwargs), a must be supplied, b has a default value so it can be left out. Both a and b can be provided as positional arguments like f(2, 3) or as keyword arguments. Any _extra_ positional arguments are collected into a tuple called args, and any _extra_ keyword arguments are collected into a dictionary called kwargs. Of course you can use any names you like. Hope this helps, -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: Argument Precedence (possible bug?)
On Sun, 05 Mar 2006 04:45:05 -0800, vbgunz wrote: PS. I could be far off with this codes purpose; to try and create an example that will house all the different possible parameters (positional, keyword, * and **) in one single def statement. This is usually a bad idea, not because Python can't cope with it, but because it is usually better to learn new things in small pieces, not one giant enormous piece. Try creating a number of small functions that do different things: def f(a, b, c): print a =, a, b =, b, c =, c def g(a=0, b=0, c=0): print a =, a, b =, b, c =, c Now call them different ways, and see what happens: f() f(1) f(1,2) f(1,2,3) f(b=2) Can you see a pattern? g() g(1) g(1,2) g(1,2,3) g(b=2) Then move on to argument collectors: def h(a, b, c=0, *d, **e): print a =, a, b =, b, c =, c print d =, d, e =, e Also, remember that positional arguments and keyword arguments aren't defined differently, they are given when you call the function. For example, suppose you have this: def function(x, y): print x + y Now you call it with positional arguments: function(3, 7) Now you call it with keyword arguments: function(x=3, y=7) Now you call it with both: function(3, y=7) All from the same definition. An argument is positional or keyword according to how it is given, not how it is defined. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to except the unexpected?
Steven D'Aprano: The OP is doing it because catching all exceptions masks bugs. There are certain exceptions which should be allowed through, as they indicate a bug in the OP's code. Normally the tactic is to catch only the exceptions you are interested in, and let everything else through, but the OP needs to catch all exceptions because there are rare exceptions which he can't predict in advance. To add to that explanation: this is in a multithreaded ZODB-application. When an unexpected exception occurs and remains uncaught, a thread terminates, causing the thread pool to wait forever since some thread is not consuming its termination request from the queue, causing the app to not terminate, causing the ZODB to remain locked, causing other apps to fail, causing havoc on my server. I don't mind this when it's caused by a bug in my code, since that creates the sense of urgency required to fix the bug. But it's annoying when it happens because of an I/O exception caused by some other guys bug on the other side of the planet :-) -- René Pijlman -- http://mail.python.org/mailman/listinfo/python-list
Re: Argument Precedence (possible bug?)
I am sorry I hung you up on a typo Peter Hansen. On line 5 *arg4 should have been *par4. I hope it makes complete sense now. Sorry. -- http://mail.python.org/mailman/listinfo/python-list
Re: Argument Precedence (possible bug?)
Please allow me some time to look at your examples. I get hung up over the smallest details because in my mind, my approach should have just worked... I learned about these parameters reading O'reilly Learning Python 2nd Edition. On page 217 of the paperback or Chapter 13.5.6 in the ebook, topic: 'Argument matching: The Gritty Details' mentions the following in verbatim... ...''' Moreover, Python internally carries out the following steps to match arguments before assignment: 1. Assign non-keyword arguments by position. 2. Assign keyword arguments by matching names. 3. Assign extra non-keyword arguments to *name tuple. 4. Assign extra keyword arguments to **name dictionary. 5. Assign default values to unassigned arguments in header. '''... As you can probably tell, I tried to follow the steps exactly, except step 5 got me lost so I tried not to question it. Anyhow, thank you very much for your time and examples. I will get back to you as soon as I am done putting your response to trial. Thank you! -- http://mail.python.org/mailman/listinfo/python-list
Inline assignments
Hi list! I'm relatively new to Python, and one thing I can't seem to get over is the lack of in-expression assignments, as present in many other languages. I'd really like to know how Python regulars solve the problems posed by that. For example, I recently wanted to do this: if callable(f = getattr(self, cmd_ + name)): # Do something with f elif callable(f = getattr(self, cmdv_ + name)): # Do something else with f However, since I can't do that in Python, I ended up using an extra local variable instead, like this: f = getattr(self, cmd_ + name) f2 = getattr(self, cmdv_ + name) if callable(f): # Do something with f elif callable(f2): # Do something with f2 Another common problem for me are while loops. I would often like to do this: while (pos = somestring.find(/)) != -1: part = somestring[:pos] somestring = somestring[pos + 1:] # Handle part However, that, too, is impossible, and I end up doing something like this: while True: pos = somestring.find(/) if pos == -1: break # ... Which is quite ugly. This might have been a bad example, since somestring.split() could be used instead, but it's still valid for other situations. How would you go about these situations? Thanks for your time! Fredrik Tolf -- http://mail.python.org/mailman/listinfo/python-list
Re: generators shared among threads
[EMAIL PROTECTED] def f() i = 0 while True: yield i i += 1 g=f() If I pass g around to various threads and I want them to always be yielded a unique value, will I have a race condition? Yes. Generators can be shared between threads, but they cannot be resumed from two threads at the same time. You should wrap it in a lock to ensure that only one thread at a time can resume the generator. Read this thread from a couple of years back about the same topic. Suggested generator to add to threading module. http://groups.google.com/group/comp.lang.python/browse_frm/thread/76aa2afa913fe4df/a2ede21f7dd78f34#a2ede21f7dd78f34 Also contained in that thread is an implementation of Queue.Queue which supplies values from a generator, and which does not require a separate thread to generate values. HTH, -- alan kennedy -- email alan: http://xhaus.com/contact/alan -- http://mail.python.org/mailman/listinfo/python-list
Re: Random Prime Generator/Modular Arithmetic
H. Well, I don't know what else I could do, except for to write a function that doesn't require recursion. Still, 300 digits isn't too bad... I have also realized that if you try is_prime(3) it will return false. I'll have to work on it... Thanks for the help! -- http://mail.python.org/mailman/listinfo/python-list
Re: Random Prime Generator/Modular Arithmetic
Also you last code which looked like: def cran_rand(min,max): if(minmax): x=max max=min min=x range=round(log(max-min)/log(256)) if range==0: range=1 num=max+1 while(nummax): num=min+s2num(urandom(range)) return num what does s2num do? im assuming it changes string chars to ascii decimal? Is that correct? and i thought is_prime would work better if you listed all small primes (2) and check if they are divisible by those. Aside from that Im really interested in your cran_rand function as I havent fully tested it out yet. Cheers Tuvas wrote: H. Well, I don't know what else I could do, except for to write a function that doesn't require recursion. Still, 300 digits isn't too bad... I have also realized that if you try is_prime(3) it will return false. I'll have to work on it... Thanks for the help! -- http://mail.python.org/mailman/listinfo/python-list
Re: Inline assignments
Fredrik Tolf wrote:
I'm relatively new to Python, and one thing I can't seem to get over is
the lack of in-expression assignments, as present in many other
languages. I'd really like to know how Python regulars solve the
problems posed by that.
For example, I recently wanted to do this:
if callable(f = getattr(self, cmd_ + name)):
# Do something with f
elif callable(f = getattr(self, cmdv_ + name)):
# Do something else with f
for prefix in ('cmd_', 'cmdv_'):
f = getattr(self, prefix + name)
if callable(f):
# do something with f
(and note that the if callable(f) test is probably not required
anyway, though that depends on the specific case)
If the do something and do something else parts are really doing
different things, then you should put that code into other methods and
include references to those methods in the list along with the prefixes,
so you can keep the code free of the extra layer of logic. A more real
example would be useful in continuing the discussion down that path.
(At the moment, the answer to that looks like it would be since you are
already looking up a callable, just call it.)
Another common problem for me are while loops. I would often like to do
this:
while (pos = somestring.find(/)) != -1:
part = somestring[:pos]
somestring = somestring[pos + 1:]
# Handle part
However, that, too, is impossible, and I end up doing something like
this:
while True:
pos = somestring.find(/)
if pos == -1: break
# ...
Which is quite ugly.
Ugly is very much in the eye of the beholder. In this case, with an eye
to readability and maintainability, I find the latter much more direct
than the former, which blends a search, and assignment, a comparison,
and a conditional control structure all into a single line, making it
very hard to just scan the code quickly and know for sure what is happening.
This might have been a bad example, since
somestring.split() could be used instead, but it's still valid for other
situations.
And each of those other situations usually has an equally
straightforward solution. :-)
-Peter
--
http://mail.python.org/mailman/listinfo/python-list
Re: Random Prime Generator/Modular Arithmetic
Yep, you guessed correctly about the s2num function, I knew I should have put a bit more.. It just converts an ascii string to a number, however many numbers that are nessicary. I could indeed check for all primes below a certain number, however, it still seems to run quite fast, at least to a 400 digit number. It's not something I'm going to use a ton, so optimizing it might not be worth it much more than it is. Perhaps I'll try all primes at least up to 100, that wouldn't be too bad... Maybe I'll have to modify my old prime string to output the python command to check all of them, it's a bit of a pain the whole if 0 in (n%2, n%3) stuff, and I can't think of a better way to do it without writing a new function to do so. I'm going to post the new code in just a minute, it's running quite nicely. I'm also posting my RSA function, which I believe should be secure enough. I'm uploading the code to them now, the HTML page'll be a few minutes... -- http://mail.python.org/mailman/listinfo/python-list
Re: Inline assignments
Fredrik Tolf wrote:
However, since I can't do that in Python, I ended up using an extra
local variable instead, like this:
f = getattr(self, cmd_ + name)
f2 = getattr(self, cmdv_ + name)
if callable(f):
# Do something with f
elif callable(f2):
# Do something with f2
If 'do something' is the same thing:
for prefix in ('cmd_', 'cmdv_'):
f = getattr(self, prefix+name)
if callable(f):
# do something with f
break
If 'do something' is different each time, put each block into a method:
def do_cmd(self, f): ...
def do_cmdv(self, f): ...
...
for prefix, action in (('cmd_', self.do_cmd), ('cmdv_', self.do_cmdv)):
f = getattr(self, prefix+name)
if callable(f):
action(f)
break
Another common problem for me are while loops. I would often like to do
this:
while (pos = somestring.find(/)) != -1:
part = somestring[:pos]
somestring = somestring[pos + 1:]
# Handle part
for part in somestring.split(/)[:-1]:
# handle part
Are you sure you didn't want to process the last part of the string as
well? I would have thought that to be more common, and rather harder to
write using your original structure.
Which is quite ugly. This might have been a bad example, since
somestring.split() could be used instead, but it's still valid for other
situations.
Not really. Your original loop refactors quite nicely by calling a method
or function which returns a sequence of results. The same pattern in will
always be refactorable in the same way. If the appropriate 'split' function
doesn't already exist then you can write it.
A very common way to rewrite this sort of loop these days is to write a
generator. It is usually beneficial to factor out the complex part of the
loop logic in this way as then you only have to write it once no matter how
many loops you have with the same structure.
--
http://mail.python.org/mailman/listinfo/python-list
Why I chose Python over Ruby
I discovered Python a few months ago and soon decided to invest time in learning it well. While surfing the net for Python, I also saw the hype over Ruby and tried to find out more about it, before I definitely embarked on studying and practicing Python. I recently found two sufficient answers for choosing Python - which is a personal choice and others may differ, but I'd like to share it anyway : 1) In Ruby there is a risk of Variable/Method Ambiguity when calling a method with no parameters without using () : Here is an excerpt from the book Programming Ruby The Pragmatic Programmer's Guide. http://www.rubycentral.com/book/language.html When Ruby sees a name such as ``a'' in an expression, it needs to determine if it is a local variable reference or a call to a method with no parameters. To decide which is the case, Ruby uses a heuristic. As Ruby reads a source file, it keeps track of symbols that have been assigned to. It assumes that these symbols are variables. When it subsequently comes across a symbol that might be either a variable or a method call, it checks to see if it has seen a prior assignment to that symbol. If so, it treats the symbol as a variable; otherwise it treats it as a method call. As a somewhat pathological case of this, consider the following code fragment, submitted by Clemens Hintze. def a print Function 'a' called\n 99 end for i in 1..2 if i == 2 print a=, a, \n else a = 1 print a=, a, \n end end OUTPUTS a=1 Function 'a' called a=99 During the parse, Ruby sees the use of ``a'' in the first print statement and, as it hasn't yet seen any assignment to ``a,'' assumes that it is a method call. By the time it gets to the second print statement, though, it has seen an assignment, and so treats ``a'' as a variable. Note that the assignment does not have to be executed---Ruby just has to have seen it. This program does not raise an error. I tried the code above at the interactive Ruby 1.8.2 interpreter : http://www.ruby.ch/tutorial/ 2) Ruby does not have true first-class functions living in the same namespace as other variables while Python does : In Python : def sayHello (name) : return Hello + name print sayHello(Mr. Bond) m = sayHello print m print m(Miss Moneypenny) OUTPUTS Hello Mr. Bond function sayHello at 0x0102E870 Hello Miss Moneypenny In Ruby you need extra syntax that ruins the first-class-ness : def sayHello (name) return Hello + name end puts sayHello(Mr. Bond) m = Class.method(:sayHello) puts m puts m.call(Miss Moneypenny) OUTPUTS Hello Mr. Bond #Method: Class(Object)#sayHello Hello Miss Moneypenny 4) Conclusion Since I did a lot of work in Scheme, rigor and consistency are most important to me, and Python certainly meets this requirement. --- Python newbie -- http://mail.python.org/mailman/listinfo/python-list
Re: Papers on Dynamic Languages
On Mar 4, 2006, at 3:00 PM, Paul Boddie wrote: I'd have a look at the following Python-related papers: Michael Salib's Starkiller paper (and presentation): http://www.python.org/pycon/dc2004/papers/1/ Mark Dufour's ShedSkin paper: http://kascade.org/optimizing_python.pdf John Aycock's Aggressive Type Inference paper: http://www.python.org/workshops/2000-01/proceedings/papers/aycock/ aycock.html I also provided a fair number of references in the following thread: http://groups.google.co.uk/group/comp.lang.python/browse_thread/ thread/cc98317bdf96efda I hope this is of use! Paul All that looks fantastic, and I'd forgotten there was a paper on Shedskin. Thanks a bunch, Jay P. -- http://mail.python.org/mailman/listinfo/python-list
Re: Inline assignments
Fredrik Tolf [EMAIL PROTECTED] wrote:
...
I'm relatively new to Python, and one thing I can't seem to get over is
the lack of in-expression assignments, as present in many other
languages. I'd really like to know how Python regulars solve the
problems posed by that.
In general, we've learned to do without and structure our code
differently -- less compactly, more airy. Python is not about
maximally compact code -- other languages of roughly equivalent power,
such as Perl, are more suitable if that's your goal; in Python, we aim
for less compactness and more readability (and maintainability). E.g.:
if callable(f = getattr(self, cmd_ + name)):
# Do something with f
elif callable(f = getattr(self, cmdv_ + name)):
# Do something else with f
might become:
f = getattr(self, cmd_ + name)
if callable(f):
# Do something with f
else:
f = getattr(self, cmdv_ + name)
if callable(f):
# Do something else with f
7 lines instead of 4 (if the comments stand for one line each), but
exactly the same semantics.
Another common problem for me are while loops. I would often like to do
That's part of why Python often prefers for loops -- with a generator to
handle the looping logic part, if needed. For example,
while (pos = somestring.find(/)) != -1:
part = somestring[:pos]
somestring = somestring[pos + 1:]
# Handle part
might often become a simple:
for part in somestring.split('/'):
# handle part
but that has slightly different semantics (handles the part after the
last occurrence of / too, doesn't explicitly record pos, ...) which
might be adjusted if needed (e.g. with a [:-1] after the call to split
and before the colon to omit the last part). If the adjustment is
major, e.g. you do need every variable to be set just like so in the
body, then a generator can help -- with the focus being on a separation
between the business logic (the handle part processing) and the
plumbing (generate all 'parts' in sequence), and the latter going in the
generator, not distracting from the handling as may happen when you mix
the two things. The business-logic part will always look like:
for pos, part in splitter(somestring, '/'):
# handle part, using pos as well
and the splitter generator is written elsewhere, a la
def splitter(somestring, separ):
while True:
pos = somestring.find(separ)
if pos == -1: break
yield pos, somestring[:pos]
somestring = somestring[pos+1:]
with the big advantage that you may change the implementation to be more
efficient, if and when needed, without touching the business logic part
which remains nestled in the nice, simple, readable for loop.
for example:
def splitter(somestring, separ):
pos = 0
while True:
nextpos = somestring.find(separ, pos)
if nextpos == -1: break
yield nextpos-pos, somestring[pos:nextpos]
pos = nextpos+1
Same semantics, less busywork, so presumably faster (the timeit module
exists to let you check the speed of code fragments, of course).
All this being said, I do sometimes find myself coding a first version
of some algorithm by following as closely as possible some published
reference code or pseudocode, before enhancing it to be clearer, more
efficient, more Pythonic, or whatever. When that happens, some syntax
sugar to assign and test in the same expression does come in handy, to
enable coding of a first version that's closer in spirit to the
non-Python reference version.
It was, of course, no trouble at all to make myself an assign and test
in the same expression snippet, and I (again, of course) published it
in the Python Cookbook (both online and printed editions) for others'
benefit. For example:
class Holder(object):
def set(self, value):
self.value = value
return value
data = Holder()
Now, with this tiny piece of plumbing adapter, you can code, e.g.:
while data.set(somestring.find(/)) != -1:
part = somestring[:data.value]
somestring = somestring[data.value + 1:]
# Handle part
Another use case for this Holder class is when you're using Python to
prototype something that you already know will need to be recoded in
another given language once it's ready -- the motivation is similar to
the one for the main use case of code as close as possible to a
published reference implementation, namely enabling Python code that is
closer to what's idiomatic in some other language than to idiomatic
Python itself.
Therein, of course, lies the danger -- over-relying on this adapter may
mean you never really learn to think the Python way and thus to code
idiomatic Python, even when that would be most appropriate (i.e., in
most cases). Still, Python _is_ a consenting adults language, so I
think it's appropriate to show how its power can easily let you keep
using idioms coming from different languages... even when that usage is
not the optimal choice that you could and should make, it's up to you.
Re: Random Prime Generator/Modular Arithmetic
Also I think the snippet code [p for p in range(2,N) if 0 not in [pow(w,p-1,p)==1 for w in [2, 3, 5, 7, 11] if pw]] is probably nicer to generate a list of primes for up to N (instead of hard coded) Aside from that looks nice. Thanks Tuvas wrote: Yep, you guessed correctly about the s2num function, I knew I should have put a bit more.. It just converts an ascii string to a number, however many numbers that are nessicary. I could indeed check for all primes below a certain number, however, it still seems to run quite fast, at least to a 400 digit number. It's not something I'm going to use a ton, so optimizing it might not be worth it much more than it is. Perhaps I'll try all primes at least up to 100, that wouldn't be too bad... Maybe I'll have to modify my old prime string to output the python command to check all of them, it's a bit of a pain the whole if 0 in (n%2, n%3) stuff, and I can't think of a better way to do it without writing a new function to do so. I'm going to post the new code in just a minute, it's running quite nicely. I'm also posting my RSA function, which I believe should be secure enough. I'm uploading the code to them now, the HTML page'll be a few minutes... -- http://mail.python.org/mailman/listinfo/python-list
dual CPU-mode in python
Hi, I have a python script which i convert to an executeable (using py2exe) and on a dual-cpu machine seems to be taking only 50% (1cpu) only. I was wondering if there is a way to maximize CPU usage without forking the function? Thanks -- http://mail.python.org/mailman/listinfo/python-list
Re: Why I chose Python over Ruby
Francois wrote: I discovered Python a few months ago and soon decided to invest time in learning it well. While surfing the net for Python, I also saw the hype over Ruby and tried to find out more about it, before I definitely embarked on studying and practicing Python. I recently found two sufficient answers for choosing Python - which is a personal choice and others may differ, but I'd like to share it anyway Thanks for sharing that. I had a gut feeling Python would be better than Ruby, but I never took the time to study Ruby. Now I do have some nice stones to throw at Ruby-fanatics ;-) Sybren -- http://mail.python.org/mailman/listinfo/python-list
Re: Random Prime Generator/Modular Arithmetic
Actually, it wasn't very nice, it returned composites instead of primes... There was alot of little bugs, I'm glad I checked it again. The new code once again is uploaded, the previews are on their way... I did set up a system to check for primality up to 1000, I think any more than that and it will become conter-productive. -- http://mail.python.org/mailman/listinfo/python-list
Re: Why I chose Python over Ruby
Francois [EMAIL PROTECTED] wrote: Since I did a lot of work in Scheme, rigor and consistency are most important to me, and Python certainly meets this requirement. It does pretty well, with some tempering of pragmatism -- but, to play devil's advocate, Ruby isn't far in this respect. In either case, you will find more rigor and consistency in good languages of a more academic bent, such as Haskell, but will surely find a lot in either Ruby or Python. The trick about distinguishing a name's exact nature based on whether the compiler sees an assignment to that name in some part of code is found in both languages, albeit in different ways. In Ruby, as you've pointed out, it's the heuristic used to disambiguate local variable access from zero-argument method calls, and the part of code is the function up to the point of access. In Python, it's used to disambiguate local from global or free variables, and the part of code is the body of the whole function (Ruby does not need to make this latter distinction because it strops global names with a leading sigil -- $a is always the global variable a, just like @a is always the instance attribute a, which we'd write self.a in Python). Another subtle case in Ruby is whether an assignment such as a=23 _within a block_ is meant to be local to the block or meant to rebind local name 'a' within the enclosing function; again, the heuristic is similar, depending only on whether the compiler had seen another assignment to a before it saw the block (Python forbids the rebinding of variables coming from an enclosing but non-global scope, to avoid facing this issue). All in all, Python is more likely with these heuristics to respect the principles (from the zen of python, import this at an interactive prompt): in face of ambiguity, refuse the temptation to guess; errors should not pass silently, unless explicitly silenced. I.e., any Python code which accidentally runs afoul of these heuristics is likely to raise an exception, alerting you to the situation. Ruby strives rather for a do what I mean ethos, and obviously some people prefer that. I also share your preference for a single namespace for callable and non-callable values, as in Python (and Scheme, Lisp, C++, ...), rather than disjoint namespaces as in Ruby (and Smalltalk), but I do not see it as a question of rigor and consistency at all -- e.g., I do not perceive Smalltalk as less rigorous or consistent than C++, on the contrary. So, I agree with your choice, and I think I understand your motivations, but I do not entirely share your motivations, personally speaking. Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: Random Prime Generator/Modular Arithmetic
Although, I have to brag quickly, adding in this simple prime check speed up the algorithm to the point that it's actually faster to find a prime number with my program than to verify a number prime with GP/PARI, so, I feel good. -- http://mail.python.org/mailman/listinfo/python-list
Re: Inline assignments
On Sun, 05 Mar 2006 15:09:28 +0100, Fredrik Tolf wrote:
Hi list!
I'm relatively new to Python, and one thing I can't seem to get over is
the lack of in-expression assignments, as present in many other
languages. I'd really like to know how Python regulars solve the
problems posed by that.
It is true that there is a whole class of bugs which Python code can't
duplicate because of the lack of in-expression assignments. Somehow
Python programmers manage to muddle along.
For example, I recently wanted to do this:
if callable(f = getattr(self, cmd_ + name)):
# Do something with f
elif callable(f = getattr(self, cmdv_ + name)):
# Do something else with f
However, since I can't do that in Python, I ended up using an extra
local variable instead, like this:
f = getattr(self, cmd_ + name)
f2 = getattr(self, cmdv_ + name)
if callable(f):
# Do something with f
elif callable(f2):
# Do something with f2
Here is one way:
f = getattr(self, cmd_ + name)
if callable(f):
# Do something with f
else:
f = getattr(self, cmdv_ + name)
if callable(f):
# do something with f
Here is another:
def handle_func(*fs):
Do something with the first callable argument.
for f in fs:
if callable(f):
# do something with f
break
L = [getattr(self, s + name) for s in (cmd_, cmdv_)]
handle_func(L)
Here is a third:
L = map(lambda s, name=name: s+name, (cmd_, cmdv_))
L = map(lambda s, me=self: getattr(me, s), L)
L = filter(callable, L)
# do something with L[0]
Or if you are really nuts, you can convert that last one to a one-liner:
# do something with:-
filter(callable, map(lambda s, me=self: getattr(me, s), map(lambda s,
name=name: s+name, (cmd_, cmdv_[0]
Or possibly think about using a different algorithm, maybe something like
this:
class Dispatcher:
def f1(self): pass
def f2(self): pass
def __init__(self):
self.fmap = {cmd_name: self.f1, cmdv_name: self.f2}
def handle_func(self, s=name):
try:
f = self.fmap[cmd_+s]
except KeyError:
f = self.fmap[cmdv_+s]
f() # or do something with f
Remember that functions and methods are first class objects, you may not
need to pass strings around, then convert the string to a function. Just
pass the function directly.
Another common problem for me are while loops. I would often like to do
this:
while (pos = somestring.find(/)) != -1:
part = somestring[:pos]
somestring = somestring[pos + 1:]
# Handle part
If you are splitting pathnames, you may be able to use os.path instead of
reinventing the wheel.
However, that, too, is impossible, and I end up doing something like
this:
while True:
pos = somestring.find(/)
if pos == -1: break
# ...
Which is quite ugly. This might have been a bad example, since
somestring.split() could be used instead, but it's still valid for other
situations.
Such as?
Here is another way:
pos = somestring.find(/)
while pos != -1:
part = somestring[:pos]
somestring = somestring[pos + 1:]
# handle part
And another:
while True:
try:
pos = somestring.index(/)
except ValueError:
break
part = somestring[:pos]
somestring = somestring[pos + 1:]
# handle part
And a third:
start = 0
while True:
try:
pos = somestring.index(/, start)
except ValueError:
break
# handle somestring[start:pos]
start = pos + 1
If you are coming from a Java background, you may consider exceptions to
be a lot of work. In Python, setting up a try...except block is very
lightweight, so long as exceptions are rare. Hitting the except clause is
more work, so you should avoid that idiom if you expect the try to raise
an exception most of the time.
--
Steven.
--
http://mail.python.org/mailman/listinfo/python-list
Re: How to except the unexpected?
Rene Pijlman wrote:
Steven D'Aprano:
The OP is doing it because catching all exceptions masks bugs. There are
certain exceptions which should be allowed through, as they indicate a bug
in the OP's code. Normally the tactic is to catch only the exceptions you
are interested in, and let everything else through, but the OP needs to
catch all exceptions because there are rare exceptions which he can't
predict in advance.
... This is in a multithreaded ZODB-application
When an unexpected exception occurs and remains uncaught, a thread
terminates,
At the base of the thread code, you could put
import sys, threading, logging
class MyThread(threading.Thread):
def run(self):
try:
threading.Thread.run(self) # or whatever
except:
etype, error, traceback = sys.exc_info()
logging.warning('Exception %s: %s seen at %s' %
(etype.__name__, error, _someformat_(traceback)))
_try_to_rescue_or remove_this_thread_
If the condition is infrequent enough. If not (if you run a real
risk of multiple threads accessing the log simultaneously), have
a queue of log messages that you feed to a single logging thread.
--
-Scott David Daniels
[EMAIL PROTECTED]
--
http://mail.python.org/mailman/listinfo/python-list
Re: raw strings and \
Hi Duncan, thanks for the reply. I figured that this was a technical problem associated with the parser. This one is going on my Python gotchas list. It is really silly from an end user perspective to have \ not special in raw strings _except_ if it is the last character. -- http://mail.python.org/mailman/listinfo/python-list
Re: lists: += vs. .append() oddness with scope of variables
Duncan Booth wrote: Sandro Dentella wrote: I'd like to understand why += operator raises an error while .append() does not. My wild guess is the parses treats them differently but I cannot understand why this depends on scope of the variables (global or class variables): Any assignment to a variable within a function means that the name to which you are assigning is regarded as a local variable (unless you use the 'global' statement to override that). += is a form of assignment, calling the append method is not an assignment. The solution here is simply to use 'global a' to tell the compiler that you meant to assign the the global variable rather than creating a new local variable. As Duncan knows but forgot to mention, eric.append(spam) doesn't write the variable eric, it simply manipulates the object that eric names. -- -Scott David Daniels [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
testing for existence of compilers/executables
I am working with my build system using scons. I would like to test the existence of 'doxygen' or any other compiler/executable in the path (like gcc/icc/...) What is the most efficient way to find this out using python? using scons? Is there a way to list all C/C++/fortran compilers available on a machine using python so that I can give my user an option to select one? Thanks a lot for your help, --j -- http://mail.python.org/mailman/listinfo/python-list
Re: Papers on Dynamic Languages
Jay Parlar wrote: All that looks fantastic, and I'd forgotten there was a paper on Shedskin. Thanks a bunch, Jay P. lots of spirited discussion at artima http://www.artima.com/forums/flat.jsp?forum=106thread=7590 http://c2.com/cgi/wiki?DuckTyping http://lambda-the-ultimate.org/node/1319 -- http://mail.python.org/mailman/listinfo/python-list
Re: dual CPU-mode in python
Astan Chee wrote: Hi, I have a python script which i convert to an executeable (using py2exe) and on a dual-cpu machine seems to be taking only 50% (1cpu) only. I was wondering if there is a way to maximize CPU usage without forking the function? Thanks Python has a global interpreter lock (GIL) that inhibits parallelism. Certain extensions will clear the lock, but generally speaking you will need to generate multiple processes to take full advantage of parallel hardware. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC/Ltd www.holdenweb.com Love me, love my blog holdenweb.blogspot.com -- http://mail.python.org/mailman/listinfo/python-list
Re: raw strings and \
[EMAIL PROTECTED] wrote: Hi Duncan, thanks for the reply. I figured that this was a technical problem associated with the parser. This one is going on my Python gotchas list. It is really silly from an end user perspective to have \ not special in raw strings _except_ if it is the last character. The alternative would have been to offer no way at all for a rawstring to include its quoting-character. Since rawstrings were designed to support regular expressions (which never need to end with a backslash), that was considered a higher cost -- there is no real advantage to supporting backslash-using Dos/Windows path literals, even though many Windowsers use rawstrings for those. Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: Random Prime Generator/Modular Arithmetic
Tuvas wrote: Okay, I don't know if your farmiliar with the miller-rabin primality test, Paul is familiar with it. When he referred to your Miller-Rabin test, he meant all the rounds. but it's what's called a probabalistic test. Meaning that trying it out once can give fake results. In the sense that some composites will pass as prime for some bases. For instance, if you use the number 31 to test if 561 is prime, you will see the results say that it isn't. That's not an instance of a fake result; Miller-Rabin has that one right. When Miller-Rabin says a number is composite, it is always correct. Your current Miller-Rabin test, in http://www.geocities.com/brp13/Python/modular.html in method Mod.is_strong_pseudo_prime(), looks buggy. Obviously you want cut() not cut, and if 1: cannot fail. In my opinion, the Mod class is not such a good idea; just use functions. Note that Python has modular exponentiation built in. pow(base, power, modulus) with positive integer arguments will return base**power % modulus. Finally, though most introductory crypto courses don't cover it, RSA requires padding of the plaintext data. Google RSA + Padding for more. Or ask on sci.crypt. -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list
Re: raw strings and \
[EMAIL PROTECTED] wrote: Hi Duncan, thanks for the reply. I figured that this was a technical problem associated with the parser. This one is going on my Python gotchas list. It is really silly from an end user perspective to have \ not special in raw strings _except_ if it is the last character. But at the parsing stage, it *is* somewhat special, even if it is not the last charater. E.g, a = r'check \' this' print a The second quote is not regarded as ending the string literal. -- http://mail.python.org/mailman/listinfo/python-list
Re: raw strings and \
On Sun, 05 Mar 2006 08:27:31 -0800, plahey wrote: Hi Duncan, thanks for the reply. I figured that this was a technical problem associated with the parser. This one is going on my Python gotchas list. It is really silly from an end user perspective to have \ not special in raw strings _except_ if it is the last character. I don't deny that this is a gotcha, but you misunderstand the purpose of raw strings. They weren't designed so that Windows users could enter pathnames with backslashes. Raw strings are designed to enter regular expressions, and for regular expressions, not being able to end a string with a backslash is not a bug but a feature. See http://www.ferg.org/projects/python_gotchas.html#contents_item_2 (and try not to choke on the oh-so-saccharine-sweet cutesy introduction. Red Ridinghood indeed *wink*) -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to except the unexpected?
Yes, and that's the Right Thing(tm) to do. Source code don't lie. Source code don't get out of sync. So source code *is* the best documentation (or at least the most accurate). I could not disagree more strongly with this. Not just no, but hell no! Yes, and that's the Right Thing(tm) to do. No, it is a horrible thing to do. But since the documentation of some modules is just plain horrible we sometimes have no choice. Source code don't lie. Source code don't get out of sync. True but implementation details change from release to release. So source code *is* the best documentation (or at least the most accurate). No, source code is the *worst possible* documentation because it makes no distinction between implementation detail and method contract. If the implementer considers the implementation to be the documentation then his/her refactoring options are significantly reduced. Typically implementers are not aware of this and they refactor anyway, breaking client code left and right. The C++ FAQ has a nice discussion of this issue. Minimally acceptable documentation consists of the following (I think this is language independent): PURPOSE: What does this method/function do REQUIRE: pre-conditions - What must have happened before calling this method (or restrictions on the domain of the inputs) PROMISE: post-conditions - What can you expect upon return or what exceptions can be thrown I consider the above to be the minimal amount of documentation that is acceptable. If you have less than that, I consider the method to be undocumented. Needless to say, I consider lots of code that I see to be undocumented. If you don't have the above, you get the problems that OP was hitting (or worse, see the C++ FAQ). I am not a huge fan of Java's ubiquitous use of checked exceptions or even of static typing but it does help supply some of the above documentation (although in a suboptimal way) that must be supplied by hand in Python. This is the dirty little secret of dynamically typed languages. It makes proper documentation even more important because method signatures supply less information. -- http://mail.python.org/mailman/listinfo/python-list
Re: dual CPU-mode in python
Astan Chee wrote: I have a python script which i convert to an executeable (using py2exe) and on a dual-cpu machine seems to be taking only 50% (1cpu) only. I was wondering if there is a way to maximize CPU usage without forking the function? it depends on what your script is doing. the GIL makes it impossible to use more than one CPU per process for byte code intensive code: http://docs.python.org/api/threads.html but code that uses I/O or C-level crunching can get around this, if the C-level code is properly written. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: raw strings and \
Hi, thanks for the reply. I was not aware of this in raw strings (and frankly, don't like it... but who cares about that :-) ) When I needed embedded quotes in a raw string I went the triple quote route: a = r'''check \' this''' which makes more sense to me. -- http://mail.python.org/mailman/listinfo/python-list
Re: raw strings and \
Hi Alex, thanks for the reply. I can see that there is a choice that needed to be made. Before I was aware of the \ issue I just used (yes it has come up, but the example is at work) triple quotes to work around the embedded quote issue: x=r'''It's like this c:\blah\ ok?''' print x It's like this c:\blah\ ok? Am I missing something? I guess my point is that it is quite surprising that r'\' is not a legal way to represent a backslash. I look for consistency in the tools that I work with and this except-for-the-last-character exception is annoying (I admit it might be a silly use-case but consistency is consistency). Again, thanks for taking the time to reply. Now get back to work on your new Nutshell book :-) -- http://mail.python.org/mailman/listinfo/python-list
Re: raw strings and \
Hi Steven, thanks for the reply. I was/am aware that raw strings are mainly used for regular expressions (and franky that was I usually use them for). I was not aware that they still have special powers in raw strings (thanks for the link!). This one bit me when I was doing some quick and dirty hacking and a 5 minute task ended up being a much longer adventure becuase of this (Note to self: don't post when annoyed). -- http://mail.python.org/mailman/listinfo/python-list
Re: Why I chose Python over Ruby
Alex Martelli wrote: I also share your preference for a single namespace for callable and non-callable values, as in Python (and Scheme, Lisp, C++, ...), rather than disjoint namespaces as in Ruby (and Smalltalk), but I do not see it as a question of rigor and consistency at all -- e.g., I do not perceive Smalltalk as less rigorous or consistent than C++, on the contrary. So, I agree with your choice, and I think I understand your motivations, but I do not entirely share your motivations, personally speaking. Thanks Alex for your excellent explanations. I have the Python Cookbook 2nd Ed., and I highly appreciate your knowledge and experience. I guess my choice of words rigor and consistency was not very good. In this context rigor meant enforcing rules (for example having to use parentheses to call a method) to prevent ambiguity rather than depending on heuristics. Also consistency meant doing things as uniformly as possible (for example always call a method with the same syntax, whether the variable referencing it is the original name or an alias). -- Francois -- http://mail.python.org/mailman/listinfo/python-list
Re: Why I chose Python over Ruby
Francois wrote: I discovered Python a few months ago and soon decided to invest time in learning it well. While surfing the net for Python, I also saw the hype over Ruby and tried to find out more about it, before I definitely embarked on studying and practicing Python. I recently found two sufficient answers for choosing Python - which is a personal choice and others may differ, but I'd like to share it anyway : 1) In Ruby there is a risk of Variable/Method Ambiguity when calling a method with no parameters without using () : snip 2) Ruby does not have true first-class functions living in the same namespace as other variables while Python does : snip 4) Conclusion snip Since I did a lot of work in Scheme, rigor and consistency are most important to me, What happened to 3)? and Python certainly meets this requirement. --- Python newbie -- http://mail.python.org/mailman/listinfo/python-list
Re: Why I chose Python over Ruby
[EMAIL PROTECTED] wrote: What happened to 3)? 4) should have read 3). I found the typo after I posted. I guess I lack rigor myself ! -- http://mail.python.org/mailman/listinfo/python-list
Re: dual CPU-mode in python
Astan Chee: I was wondering if there is a way to maximize CPU usage Fork a Java app :-) -- René Pijlman -- http://mail.python.org/mailman/listinfo/python-list
Re: Python advocacy in scientific computation
Robert Kern wrote: 1. Write grant proposals. 2. Advise and teach students. Sorry I forgot the part about writing grant applications. As for teaching students, I have thankfully not been bothered with that too much. Yes, and this is why you will keep saying, My simulation is running too slowly, and My simulation is running out of memory. All the vectorization you do won't make a quadratic algorithm run in O(n log(n)) time. Knowing the right algorithm and the right data structures to use will save you programming time and execution time. Time is money, remember, and every hour you spend tweaking Matlab code to get an extra 5% of speed is just so much grant money down the drain. Yes, and that is why I use C (that is ISO C99, not ANSI C98) instead of Matlab for everything except trivial tasks. The design of Matlab's language is fundamentally flawed. I once wrote a tutorial on how to implement things like lists and trees in Matlab (using functional programming, e.g. using functions to represent list nodes), but it's just a toy. And as Matlab's run-time does reference counting insted of proper garbage collection, any datastructure more complex than arrays are sure to leak memory (I believe Python also suffered from this as some point). Matlab is not useful for anything except plotting data quickly. And as for the expensive license, I am not sure its worth it. I have been considering a move to Scilab for some time, but it too carries the burden of working with a flawed language. -- http://mail.python.org/mailman/listinfo/python-list
Python version of XMLUnit?
I have found XMLUnit to be very helpful for testing Java and Jython code that generates XML. At its heart XMLUnit is an XML-aware diff - it parses expected and actual XML and pinpoints any differences. It is smart enough to ignore things like attribute order, different quoting and escaping styles, and insignificant whitespace. Now I am working on a CPython project and have a similar need. Is there any comparable tool for Python? Basically I'm looking for a tool to compare XML and show diffs in an intelligible fashion that is usable from Python unit tests (using py.test, if it matters). Thanks, Kent http://xmlunit.sourceforge.net/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Python advocacy in scientific computation
David Treadwell wrote: My ability to think of data structures was stunted BECAUSE of Fortran and BASIC. It's very difficult for me to give up my bottom-up programming style, even though I write better, clearer and more useful code when I write top-down. That is also the case with Matlab, anything mor complex than an array is beyond reach. I think it was Paul Graham (the LISP guru) once claimed he did not miss recursive functions while working with Fortran 77. The limitations of a language does stunt your mind. To that extent I am happy I learned to program with Pascal and not Fortran or Matlab. S.M. -- http://mail.python.org/mailman/listinfo/python-list
Re: is there such a built-in funciton, similar to filter
Michael Hoffman [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] wcc wrote: Beginner learning Python here. I know filter(lambda x: x 3, [1, 2, 5, -3, 4, 8]) will give me a list [5, 4, 8]. What if I only need to find the first item in the list that returns Ture when applying the filter function. In this case, I only want to get the 5, and its index You have made two important changes to the function return value. Filter returns a list of items. You want an item and index. What if there is no first item? 2. Is there a built-in function, or function from a module for that? I think it is not hard to write a function for this. But knowing Python is battery included, I thought I'd like to ask. A 'battery' is something like the email, html, xml modules that assist major application areas. Not every easily written 3-line function ;-) You can use a generator expression like this: items = [1, 2, 5, -3, 4, 8] ((index, item) for index, item in enumerate(items) if item 3).next() (2, 5) items = [0,1,2,3] ((index, item) for index, item in enumerate(items) if item 3).next() Traceback (most recent call last): File pyshell#82, line 1, in -toplevel- ((index, item) for index, item in enumerate(items) if item 3).next() StopIteration I believe ifilter from the itertools module will act the same. Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: Random Prime Generator/Modular Arithmetic
Bryan Olson wrote: Tuvas wrote: Okay, I don't know if your farmiliar with the miller-rabin primality test, Paul is familiar with it. When he referred to your Miller-Rabin test, he meant all the rounds. but it's what's called a probabalistic test. Meaning that trying it out once can give fake results. In the sense that some composites will pass as prime for some bases. For instance, if you use the number 31 to test if 561 is prime, you will see the results say that it isn't. That's not an instance of a fake result; Miller-Rabin has that one right. When Miller-Rabin says a number is composite, it is always correct. I mis-stated. If you try 31 in the Miller-Rabin test. Mod(31,561).is_strong_pseudo_prime() True However, 561 is not prime, it is divisible by 3, 11, and 17. Actually, I did another test, and realized that it was indeed a bug in the code. Yikes. Oh well, thanks for the help in identifying it! An example that would be alot easier is this: Mod(16,561).is_strong_pseudo_prime() True Your current Miller-Rabin test, in http://www.geocities.com/brp13/Python/modular.html in method Mod.is_strong_pseudo_prime(), looks buggy. Obviously you want cut() not cut, and if 1: cannot fail. In my opinion, the Mod class is not such a good idea; just use functions. The reason for the modulos class, well, was more of a practice than anything else. I could indeed just use functions, but I needed the Mod class for a few other things, and figured it was just easier to program it once and use it for anything rather than anything else. Note that Python has modular exponentiation built in. pow(base, power, modulus) Nice to see that Python supports modular exponentiation. I'll have to remember that one. Probably the next time I do an update to the code, I'll just use it instead, it's probably faster than mine. with positive integer arguments will return base**power % modulus. Finally, though most introductory crypto courses don't cover it, RSA requires padding of the plaintext data. Google RSA + Padding for more. Or ask on sci.crypt. -- --Bryan Overall, I guess another update is coming soon. Thanks for the help in debuging again! -- http://mail.python.org/mailman/listinfo/python-list
Re: Why I chose Python over Ruby
Alex Martelli wrote: I also share your preference for a single namespace for callable and non-callable values, as in Python (and Scheme, Lisp, C++, ...), rather than disjoint namespaces as in Ruby (and Smalltalk), but I do not see it as a question of rigor and consistency at all -- e.g., I do not perceive Smalltalk as less rigorous or consistent than C++, on the contrary. So, I agree with your choice, and I think I understand your motivations, but I do not entirely share your motivations, personally speaking. Thanks Alex for your excellent explanations. I have the Python Cookbook 2nd Ed., and I highly appreciate your knowledge and experience. I guess my choice of words rigor and consistency was not very good. In this context rigor meant enforcing rules (for example having to use parentheses to call a function) to prevent ambiguity rather than depending on heuristics. Also consistency meant doing things as uniformly as possible (for example always call a function with the same syntax, whether the variable referencing it is the original name or an alias). -- Francois -- http://mail.python.org/mailman/listinfo/python-list
Re: Python advocacy in scientific computation
$ rm `find . -name *.pyc` Ouch. Is that a true story? While we're remeniscing about bad typos and DEC, I should tell the story about the guy who clobberred his work because his English wasn't very strong. Under RT-11, all file management was handled by a program called PIP. For example to get a list of files in the current working directory you would enter PIP *.* /LI . Well this fellow, from one of those countries where our long e sound is their i sound, mournfully announced I vanted a deerectory so I typed 'PIP *.* /DE' That one is true. mt -- http://mail.python.org/mailman/listinfo/python-list
what am I missing (syntax error)
Here's a section of code: for x in occupants: if x not in uniqueUsers and not in staff: uniqueUsers.append(x) elif x in staff and not in uniqueStaff: uniqueStaff.append(x) When I try to import the module with the function definition that contains this code, I get a syntax error pointing to the 'in' after the 'and not in staff'. I can't figure out why this is bad syntax. Both 'uniqueUsers' and 'staff' are lists. thanks for your help! -- http://mail.python.org/mailman/listinfo/python-list
Re: lists: += vs. .append() oddness with scope of variables
Sandro Dentella [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] I'd like to understand why += operator raises an error while .append() does not. Your mistake is thinking of '+=' as an operator. In Python terms it is not, any more than '=' is. In Python, neither 'a=b' nor 'a+=b' is an expression. Both symbols are statement symbols that define assigment statements (augmented in the former case). a.append(b) is an expression with side effects used as a statement. Traceback (most recent call last): File c1.py, line 26, in ? x = foo() File c1.py, line 7, in __init__ print a: , a UnboundLocalError: local variable 'a' referenced before assignment This is the clue that you did not get. It tells you that the parser thinks 'a' is local, which means you rebound the name 'a' *somewhere* in the function, even if not as obviously as a simple assignment a = whatever. It turns out that augmented assignment statements are assignments statements ;-). Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: raw strings and \
[EMAIL PROTECTED] wrote: thanks for the reply. I can see that there is a choice that needed to be made. Before I was aware of the \ issue I just used (yes it has come up, but the example is at work) triple quotes to work around the embedded quote issue: x=r'''It's like this c:\blah\ ok?''' print x It's like this c:\blah\ ok? Am I missing something? No, triplequotes are perfectly valid. I guess my point is that it is quite surprising that r'\' is not a legal way to represent a backslash. I look for consistency in the tools that I work with and this except-for-the-last-character exception is annoying (I admit it might be a silly use-case but consistency is consistency). Alas, somebody will now quote Emerson at you, I fear;-). Me, I appreciate consistency and regularity more than most (without making a fetish of it), but the rule a rawstring cannot end with an odd number of backslashes is perfectly regular and consistent, so I'm not perturbed by it (it's NOT about the last character, as r'\\' is just fine even though its last character is a \ -- it's about the parity of the length of the terminating sequence of backslashes: even is OK [0 is of course even;-)] and odd is not). Again, thanks for taking the time to reply. Now get back to work on your new Nutshell book :-) Yep, good point!-) Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: Why I chose Python over Ruby
Francois [EMAIL PROTECTED] wrote: ... I guess my choice of words rigor and consistency was not very good. In this context rigor meant enforcing rules (for example having to use parentheses to call a method) to prevent ambiguity rather than depending on heuristics. Also consistency meant doing things as uniformly as possible (for example always call a method with the same syntax, whether the variable referencing it is the original name or an alias). Ah yes, these are definitely valid nuances for the terms you've used, I admit that. Python's yearning for only one obvious way to do something, even though it's a goal to aim for rather than a reality in every case, surely does play towards these preferences, while Ruby (not quite as much as Perl, but still) has a more exhuberant approach, where having multiple obvious ways to do the same thing is seen as a plus, not a minus (a classic tiny example is the ability to get the number of items of an array a by EITHER a.size or a.length, just like for a C++ std::string, with no difference whatsoever among the two synonyms). So, I'm NOT saying your word choice was not very good: you used words who do mean what you intend (among other meanings, but then, that's the curse AND blessing of natural language;-). But anyway, thanks for the clarification! Maybe uniformity (though it, too, may suggest different and not accurate things) could be usefully added to help communicate your intended meaning (or maybe, for most people, if they hear all of rigor, consistency, uniformity, would think of some Nazi language woefully constraining their expression...?-) Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: Why I chose Python over Ruby
[EMAIL PROTECTED] [EMAIL PROTECTED] wrote: ... 1) In Ruby there is a risk of Variable/Method Ambiguity when calling ... 2) Ruby does not have true first-class functions living in the same ... 4) Conclusion ... What happened to 3)? I thought the OP was counting up by powers of 2 to indicate the exponential nature of the issues...;-) Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: Python advocacy in scientific computation
Michael Tobis wrote: $ rm `find . -name *.pyc` Ouch. Is that a true story? Yup. Fortunately, it was a small, purely personal project, so it was no huge loss. It was enough for me to start using CVS on my small, purely personal projects, though! -- Robert Kern [EMAIL PROTECTED] 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: what am I missing (syntax error)
Try: for x in occupants: if x not in uniqueUsers and x not in staff: uniqueUsers.append(x) elif x in staff and x not in uniqueStaff: uniqueStaff.append(x) -- http://mail.python.org/mailman/listinfo/python-list
Re: what am I missing (syntax error)
orangeDinosaur [EMAIL PROTECTED] wrote: Here's a section of code: for x in occupants: if x not in uniqueUsers and not in staff: uniqueUsers.append(x) elif x in staff and not in uniqueStaff: uniqueStaff.append(x) When I try to import the module with the function definition that contains this code, I get a syntax error pointing to the 'in' after the 'and not in staff'. I can't figure out why this is bad syntax. Both 'uniqueUsers' and 'staff' are lists. say ...'and x not in staff' -- you need the x between 'and' and 'not', and similarly for the elif (and don't use tabs -- they make a mess of a display on many newsreaders etc -- fixed to spaces above). Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: what am I missing (syntax error)
orangeDinosaur wrote: Here's a section of code: for x in occupants: if x not in uniqueUsers and not in staff: uniqueUsers.append(x) elif x in staff and not in uniqueStaff: uniqueStaff.append(x) When I try to import the module with the function definition that contains this code, I get a syntax error pointing to the 'in' after the 'and not in staff'. I can't figure out why this is bad syntax. Both 'uniqueUsers' and 'staff' are lists. thanks for your help! I think you're missing an 'x': for x in occupants: if x not in Users and x not in Staff: Users.append(x) Gerard -- http://mail.python.org/mailman/listinfo/python-list
Re: what am I missing (syntax error)
orangeDinosaur [EMAIL PROTECTED] writes: Here's a section of code: for x in occupants: if x not in uniqueUsers and not in staff: uniqueUsers.append(x) elif x in staff and not in uniqueStaff: uniqueStaff.append(x) When I try to import the module with the function definition that contains this code, I get a syntax error pointing to the 'in' after the 'and not in staff'. I can't figure out why this is bad syntax. Both 'uniqueUsers' and 'staff' are lists. The question is: what's not in XXX? x? Something else? You hve to remember that the computer does only what you tell it to do: if x not in uniqueUsers and x not in staff: ... I also prefer using parenthesis to make things more clear and avoid precedence surprises. -- Jorge Godoy [EMAIL PROTECTED] Quidquid latine dictum sit, altum sonatur. - Qualquer coisa dita em latim soa profundo. - Anything said in Latin sounds smart. -- http://mail.python.org/mailman/listinfo/python-list
beginner question on dinamin buiding of arg list
I need to build-up an arg list to pass to a function.
Suppose I have a dictionary:
opts = { 'user' : 'jack', 'addr' : 'Green Str.'}
and I want to build a cmd line like this:
select( user='jack', addr='Green Str.' )
I'm clueless...
TIA
sandro
*:-)
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Sandro Dentella *:-)
http://www.tksql.orgTkSQL Home page - My GPL work
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Re: Python advocacy in scientific computation
sturlamolden [EMAIL PROTECTED] wrote: just a toy. And as Matlab's run-time does reference counting insted of proper garbage collection, any datastructure more complex than arrays are sure to leak memory (I believe Python also suffered from this as some point). Yes, that was fixed in the move from 1.5.2 to 2.0 (I don't recall if the intermediate short-lived 1.6 also fixed it, but nobody used that anyway;-). Matlab is not useful for anything except plotting data quickly. And as for the expensive license, I am not sure its worth it. I have been considering a move to Scilab for some time, but it too carries the burden of working with a flawed language. There was a pyscilab once, still around at http://pdilib.sourceforge.net/, but I don't think it ever matured beyond a proof of concept release 0.1 or something. Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: beginner question on dinamin buiding of arg list
Sandro Dentella [EMAIL PROTECTED] wrote:
I need to build-up an arg list to pass to a function.
Suppose I have a dictionary:
opts = { 'user' : 'jack', 'addr' : 'Green Str.'}
and I want to build a cmd line like this:
select( user='jack', addr='Green Str.' )
select(**opts)
should fit the bill. (it.comp.lang.python is the Italian newsgroup
about Python, by the way;-).
Alex
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Re: what am I missing (syntax error)
OK, thanks! -- http://mail.python.org/mailman/listinfo/python-list
Re: Python advocacy in scientific computation
Brian Blais wrote: Robert Kern wrote: That said, we have an excellent array object far superior to Matlab's. http://numeric.scipy.org/ I'd like to ask, being new to python, in which ways is this array object far superior to Matlab's? (I'm not being sarcastic, I really would like to know!) Matlab takes the view that everything is a rank-2 matrix of floating point values. Our arrays have been N-dimensional since day one. They really are arrays, not matrices. You have complete control over the types. -- Robert Kern [EMAIL PROTECTED] 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
Separating elements from a list according to preceding element
I'm having a bit of trouble with this so any help would be gratefully recieved... After splitting up a url I have a string of the form 'tag1+tag2+tag3-tag4', or '-tag1-tag2' etc. The first tag will only be preceeded by an operator if it is a '-', if it is preceded by nothing, '+' is to be assumed. Using re.split, I can generate a list that looks thus: ['tag1', '+', 'tag2', '+', 'tag3', '-', 'tag4'] I wish to derive two lists - each containing either tags to be included, or tags to be excluded. My idea was to take an element, examine what element precedes it and accordingly, insert it into the relevant list. However, I have not been successful. Is there a better way that I have not considered? If this method is suitable, how might I implement it? Thanks all, Rob Cowie -- http://mail.python.org/mailman/listinfo/python-list
Re: Python advocacy in scientific computation
sturlamolden wrote: Robert Kern wrote: Yes, and this is why you will keep saying, My simulation is running too slowly, and My simulation is running out of memory. All the vectorization you do won't make a quadratic algorithm run in O(n log(n)) time. Knowing the right algorithm and the right data structures to use will save you programming time and execution time. Time is money, remember, and every hour you spend tweaking Matlab code to get an extra 5% of speed is just so much grant money down the drain. Yes, and that is why I use C (that is ISO C99, not ANSI C98) instead of Matlab for everything except trivial tasks. The design of Matlab's language is fundamentally flawed. I once wrote a tutorial on how to implement things like lists and trees in Matlab (using functional programming, e.g. using functions to represent list nodes), but it's just a toy. And as Matlab's run-time does reference counting insted of proper garbage collection, any datastructure more complex than arrays are sure to leak memory (I believe Python also suffered from this as some point). Python still uses reference counting and has several very good data structures more complex than arrays. And yet, most programs don't leak memory. Matlab is not useful for anything except plotting data quickly. And as for the expensive license, I am not sure its worth it. I have been considering a move to Scilab for some time, but it too carries the burden of working with a flawed language. And you need to ask why Python is a better Matlab than Matlab? -- Robert Kern [EMAIL PROTECTED] 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: django and mod_python
your suggestions worked. thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: Separating elements from a list according to preceding element
Rob Cowie wrote: I'm having a bit of trouble with this so any help would be gratefully recieved... After splitting up a url I have a string of the form 'tag1+tag2+tag3-tag4', or '-tag1-tag2' etc. The first tag will only be preceeded by an operator if it is a '-', if it is preceded by nothing, '+' is to be assumed. Using re.split, I can generate a list that looks thus: ['tag1', '+', 'tag2', '+', 'tag3', '-', 'tag4'] I wish to derive two lists - each containing either tags to be included, or tags to be excluded. My idea was to take an element, examine what element precedes it and accordingly, insert it into the relevant list. However, I have not been successful. Is there a better way that I have not considered? If this method is suitable, how might I implement it? Thanks all, Rob Cowie a = [ '+', 'tag1', '+', 'tag2', '-', 'tag3', '+', 'tag4' ] import itertools b = list(itertools.islice(a,0,8,2)) c = list(itertools.islice(a,1,8,2)) result1 = [x[1] for x in itertools.izip(b,c) if x[0] == '+'] result2 = [x[1] for x in itertools.izip(b,c) if x[0] == '-'] print print result1 print result2 Gerard -- http://mail.python.org/mailman/listinfo/python-list
Re: Separating elements from a list according to preceding element
Rob Cowie wrote: I wish to derive two lists - each containing either tags to be included, or tags to be excluded. My idea was to take an element, examine what element precedes it and accordingly, insert it into the relevant list. However, I have not been successful. Is there a better way that I have not considered? Maybe. You could write a couple regexes, one to find the included tags, and one for the excluded, then run re.findall on them both. But there's nothing fundamentally wrong with your method. If this method is suitable, how might I implement it? tags = ['tag1', '+', 'tag2', '+', 'tag3', '-', 'tag4'] include, exclude = [], [] op = '+' for cur in tags: if cur in '+-': op = cur else: if op == '+': include.append(cur) else: exclude.append(cur) --Ben -- http://mail.python.org/mailman/listinfo/python-list
Re: Separating elements from a list according to preceding element
Gerard Flanagan wrote: Rob Cowie wrote: I'm having a bit of trouble with this so any help would be gratefully recieved... After splitting up a url I have a string of the form 'tag1+tag2+tag3-tag4', or '-tag1-tag2' etc. The first tag will only be preceeded by an operator if it is a '-', if it is preceded by nothing, '+' is to be assumed. Using re.split, I can generate a list that looks thus: ['tag1', '+', 'tag2', '+', 'tag3', '-', 'tag4'] I wish to derive two lists - each containing either tags to be included, or tags to be excluded. My idea was to take an element, examine what element precedes it and accordingly, insert it into the relevant list. However, I have not been successful. Is there a better way that I have not considered? If this method is suitable, how might I implement it? Thanks all, Rob Cowie a = [ '+', 'tag1', '+', 'tag2', '-', 'tag3', '+', 'tag4' ] import itertools b = list(itertools.islice(a,0,8,2)) c = list(itertools.islice(a,1,8,2)) result1 = [x[1] for x in itertools.izip(b,c) if x[0] == '+'] result2 = [x[1] for x in itertools.izip(b,c) if x[0] == '-'] print print result1 print result2 Gerard '8' is the length of 'a' (len(a)) -- http://mail.python.org/mailman/listinfo/python-list
Re: Python advocacy in scientific computation
Robert Kern wrote: And you need to ask why Python is a better Matlab than Matlab? First there are a few things I don't like: 1. Intendation as a part of the syntax, really annoying. 2. The self.something syntax is really tedious (look to ruby)! 4. Multithreading and parallel execution is impossible AFAIK because of the so-called GIL (global interpreter lock). Matlab is perhaps even worse in this respect. 5. I don't like numpy's array slicing. Array operations should be a part of the language, as in Matlab, Fortran 90, Ada 95, D, Octave. And there is a couple of questions I need answered: 1. Can python do pass by reference? Are datastructures represented by references as in Java (I don't know yet). 2. How good is matplotlib/pylab? I tried to install it but only get error messages so I haven't tested it. But plotting capabilities is really major issue. 3. Speed. I haven't seen any performance benchmarks that actually deals with things that are important for scientific programs. 4. Are there easy to use libraries containing other stuff important for scientific programs, e.q. linear algebra (LU, SVD, Cholesky), Fourier transforms, etc. E.g. in Matlab I can just type, [u,s,v] = svd(x) % which calls LAPACK linked to ATLAS or vendor-optimized BLAS Even though the language itself is very limited this type of library functionality more than makes up for it. I have looked for alternatives to Matlab for quite a while, mainly due to the cost, the åpoor speed and poor memory management. I am not sure it is Python but so far I have not found anything mor promising either. -- http://mail.python.org/mailman/listinfo/python-list
Re: Separating elements from a list according to preceding element
Rob Cowie wrote: I'm having a bit of trouble with this so any help would be gratefully recieved... After splitting up a url I have a string of the form 'tag1+tag2+tag3-tag4', or '-tag1-tag2' etc. The first tag will only be preceeded by an operator if it is a '-', if it is preceded by nothing, '+' is to be assumed. Using re.split, I can generate a list that looks thus: ['tag1', '+', 'tag2', '+', 'tag3', '-', 'tag4'] I wish to derive two lists - each containing either tags to be included, or tags to be excluded. My idea was to take an element, examine what element precedes it and accordingly, insert it into the relevant list. However, I have not been successful. Is there a better way that I have not considered? If this method is suitable, how might I implement it? Thanks all, Rob Cowie Unclever way: alist = ['tag1', '+', 'tag2', '+', 'tag3', '-', 'tag4'] include, disinclude = [], [] aniter = iter(alist) if len(alist) % 2: include.append(aniter.next()) for asign in aniter: if asign == '+': include.append(aniter.next()) else: disinclude.append(aniter.next()) A cleverer way will probably use list comprehension and logic shortcutting. James -- http://mail.python.org/mailman/listinfo/python-list
Re: Separating elements from a list according to preceding element
Gerard Flanagan wrote: Rob Cowie wrote: I'm having a bit of trouble with this so any help would be gratefully recieved... After splitting up a url I have a string of the form 'tag1+tag2+tag3-tag4', or '-tag1-tag2' etc. The first tag will only be preceeded by an operator if it is a '-', if it is preceded by nothing, '+' is to be assumed. Using re.split, I can generate a list that looks thus: ['tag1', '+', 'tag2', '+', 'tag3', '-', 'tag4'] I wish to derive two lists - each containing either tags to be included, or tags to be excluded. My idea was to take an element, examine what element precedes it and accordingly, insert it into the relevant list. However, I have not been successful. Is there a better way that I have not considered? If this method is suitable, how might I implement it? Thanks all, Rob Cowie a = [ '+', 'tag1', '+', 'tag2', '-', 'tag3', '+', 'tag4' ] import itertools b = list(itertools.islice(a,0,8,2)) c = list(itertools.islice(a,1,8,2)) result1 = [x[1] for x in itertools.izip(b,c) if x[0] == '+'] result2 = [x[1] for x in itertools.izip(b,c) if x[0] == '-'] print print result1 print result2 Gerard Unfortunately this does not address the complete specification: a = [ 'tag1', '+', 'tag2', '-', 'tag3', '+', 'tag4' ] import itertools b = list(itertools.islice(a,0,len(a),2)) c = list(itertools.islice(a,1,len(a),2)) result1 = [x[1] for x in itertools.izip(b,c) if x[0] == '+'] result2 = [x[1] for x in itertools.izip(b,c) if x[0] == '-'] print print result1 [] print result2 [] Need to check for the absence of that first op. James -- http://mail.python.org/mailman/listinfo/python-list
Re: Separating elements from a list according to preceding element
Rob Cowie a écrit :
I'm having a bit of trouble with this so any help would be gratefully
recieved...
After splitting up a url I have a string of the form
'tag1+tag2+tag3-tag4', or '-tag1-tag2' etc. The first tag will only be
preceeded by an operator if it is a '-', if it is preceded by nothing,
'+' is to be assumed.
Using re.split, I can generate a list that looks thus:
['tag1', '+', 'tag2', '+', 'tag3', '-', 'tag4']
I wish to derive two lists - each containing either tags to be
included, or tags to be excluded. My idea was to take an element,
examine what element precedes it and accordingly, insert it into the
relevant list. However, I have not been successful.
Is there a better way that I have not considered?
If you're responsible for the original URL, you may consider rewriting
it this way:
scheme://domain.tld/resource?tag1=1tag2=1tag3=1tag4=0
Else - and after you've finished cursing the guy that came out with such
an innovative way to use url parameters - I think the first thing to do
would be to fix the implicit-first-operator-mess, so you have something
consistent:
if the_list[0] != -:
the_list.insert(0, +)
Then a possible solution could be:
todo = {'+' : [], '-' : []}
for op, tag in zip(the_list[::2], the_list[1::2]):
todo[op].append(tag)
But there's surely something better...
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Re: Separating elements from a list according to preceding element
Bruno Desthuilliers wrote:
Rob Cowie a écrit :
I'm having a bit of trouble with this so any help would be gratefully
recieved...
After splitting up a url I have a string of the form
'tag1+tag2+tag3-tag4', or '-tag1-tag2' etc. The first tag will only be
preceeded by an operator if it is a '-', if it is preceded by nothing,
'+' is to be assumed.
Using re.split, I can generate a list that looks thus:
['tag1', '+', 'tag2', '+', 'tag3', '-', 'tag4']
I wish to derive two lists - each containing either tags to be
included, or tags to be excluded. My idea was to take an element,
examine what element precedes it and accordingly, insert it into the
relevant list. However, I have not been successful.
Is there a better way that I have not considered?
If you're responsible for the original URL, you may consider rewriting
it this way:
scheme://domain.tld/resource?tag1=1tag2=1tag3=1tag4=0
Else - and after you've finished cursing the guy that came out with such
an innovative way to use url parameters - I think the first thing to do
would be to fix the implicit-first-operator-mess, so you have something
consistent:
if the_list[0] != -:
the_list.insert(0, +)
Then a possible solution could be:
todo = {'+' : [], '-' : []}
for op, tag in zip(the_list[::2], the_list[1::2]):
todo[op].append(tag)
But there's surely something better...
Fabulous. Here is a fix:
the_list = ['+'] * (len(the_list) % 2) + the_list
todo = {'+' : [], '-' : []}
for op, tag in zip(the_list[::2], the_list[1::2]):
todo[op].append(tag)
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Re: Python advocacy in scientific computation
sturlamolden wrote: First there are a few things I don't like: 1. Intendation as a part of the syntax, really annoying. Each to his own. I find having the compiler enforce indentation rules is a real benefit. There's nothing quite so annoying as having 'coding standards' you are supposed to be following which aren't enforced (so nobody else working on the code followed them either). C code which never executes a for loop because of a spurious ';' can be pretty annoying too. 2. The self.something syntax is really tedious (look to ruby)! I find it really useful to use a similar style when programming in other languages such as Java or C#. In particular it means that you can instantly see when you are referring to a member variable (without having to prefix them all with m_ or some other abomination) and when you have method arguments which get assigned to member variables you don't have to think of different names for each. 4. Multithreading and parallel execution is impossible AFAIK because of the so-called GIL (global interpreter lock). Matlab is perhaps even worse in this respect. Multithreading and parallel execution work fine. The only problem is that you don't get the full benefit when you have multiple processors. This one will become more of an annoyance in the future though as more systems have hyperthreading and multi-core processors. And there is a couple of questions I need answered: 1. Can python do pass by reference? Are datastructures represented by references as in Java (I don't know yet). Python only does pass by reference, although it is more normally referred to as pass by object reference to distinguish it from language where the references refer to variables rather than objects. What it doesn't do is let you rebind a variable in the caller's scope which is what many people expect as a consequence of pass by reference. If you pass an object to a function (and in Python *every* value is an object) then when you mutate the object the changes are visible to everything else using the same object. Of course, some objects aren't mutable so it isn't that easy to tell that they are always passed by reference. -- http://mail.python.org/mailman/listinfo/python-list
