RE: Python #ifdef
Date: Mon, 3 Jun 2013 12:05:49 +1000 Subject: Re: Python #ifdef From: ros...@gmail.com To: python-list@python.org [...] Ah. I actually wasn't aware of m4's use with sendmail. I first met it as the aforementioned PHP preprocessor, simply by Googling for something along the lines of generic preprocessor. First hit solved my problems. ChrisA Why didn't you use something like EZT[1]? [1] https://code.google.com/p/ezt/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On Tue, Jun 4, 2013 at 8:18 AM, Carlos Nepomuceno carlosnepomuc...@outlook.com wrote: Date: Mon, 3 Jun 2013 12:05:49 +1000 Subject: Re: Python #ifdef From: ros...@gmail.com To: python-list@python.org [...] Ah. I actually wasn't aware of m4's use with sendmail. I first met it as the aforementioned PHP preprocessor, simply by Googling for something along the lines of generic preprocessor. First hit solved my problems. ChrisA Why didn't you use something like EZT[1]? [1] https://code.google.com/p/ezt/ I'm a bit behind getting to this; I think some python-list posts got stuck somewhere (maybe in the news-list gateway?). Anyway: The reason I didn't was simply that m4 came up first. I was familiar with the C preprocessor and PPWizard (which is designed for HTML), and simply went looking for a generic one. And yes, I had seriously contemplated using the C preprocessor (from gcc), but there was a reason not to (don't remember now, but I'm guessing it'll be the conflict between hash comments in PHP and hash directives to cpp). ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On 05/29/2013 08:05 AM, Chris Angelico wrote: It's not a bad tool. I used it as a sort of PHP preprocessor, because requirements at work had me wanting to have a source file defining a PHP class and having an autogenerated section in the middle of that class. PHP's 'include' directive doesn't work for that. Of course, had we been using a better language, that wouldn't have been an issue (and it stopped being an issue when we improved the design and stopped using that class system, too, though I retained the makefile directives about building .php.m4 - .php files). But still, GNU M4 is a decent piece of technology. Agreed. The terror that most people feel when hearing m4 is because m4 was associated with sendmail, not because m4 was inherently awful. It has problems, but you'd only encounter them when doing something _very_ abstract. -- Erik Max Francis m...@alcyone.com http://www.alcyone.com/max/ San Jose, CA, USA 37 18 N 121 57 W AIM/Y!M/Jabber erikmaxfrancis Substance is one of the greatest of our illusions. -- Sir Arthur Eddington -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
In article n4mdnzkiorrtrjbmnz2dnuvz5godn...@giganews.com, Erik Max Francis m...@alcyone.com wrote: On 05/29/2013 08:05 AM, Chris Angelico wrote: It's not a bad tool. I used it as a sort of PHP preprocessor, because requirements at work had me wanting to have a source file defining a PHP class and having an autogenerated section in the middle of that class. PHP's 'include' directive doesn't work for that. Of course, had we been using a better language, that wouldn't have been an issue (and it stopped being an issue when we improved the design and stopped using that class system, too, though I retained the makefile directives about building .php.m4 - .php files). But still, GNU M4 is a decent piece of technology. Agreed. The terror that most people feel when hearing m4 is because m4 was associated with sendmail Aggghhh. You had to go and dredge up those bad memories? I hadn't thought about sendmail config files in years. I'll probably never be able to get to sleep tonight. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
The terror that most people feel when hearing m4 is because m4 was associated with sendmail, not because m4 was inherently awful. In fact, m4 made sendmail configs easier to maintain. Skip -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On Mon, Jun 3, 2013 at 9:57 AM, Erik Max Francis m...@alcyone.com wrote: On 05/29/2013 08:05 AM, Chris Angelico wrote: It's not a bad tool. I used it as a sort of PHP preprocessor, because requirements at work had me wanting to have a source file defining a PHP class and having an autogenerated section in the middle of that class. PHP's 'include' directive doesn't work for that. Of course, had we been using a better language, that wouldn't have been an issue (and it stopped being an issue when we improved the design and stopped using that class system, too, though I retained the makefile directives about building .php.m4 - .php files). But still, GNU M4 is a decent piece of technology. Agreed. The terror that most people feel when hearing m4 is because m4 was associated with sendmail, not because m4 was inherently awful. It has problems, but you'd only encounter them when doing something _very_ abstract. Ah. I actually wasn't aware of m4's use with sendmail. I first met it as the aforementioned PHP preprocessor, simply by Googling for something along the lines of generic preprocessor. First hit solved my problems. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On 2013-05-28, Carlos Nepomuceno carlosnepomuc...@outlook.com wrote: How do you have invalid@invalid.invalid instead of your email address? I have this in my .slrnrc: set hostname invalid.invalid set username grant set realname Grant Edwards I'm not sure why it doesn't show up as grant@invalid.invalid -- I think it used to. Since I'm this as a Usenet news group using the slrn newsreader program, there's no need to make my email address visible in the message headers in a usable form. I originally did this long ago (probably 20 years) to avoid spam. I'm pretty sure that it's all in vain these days, and the spam filters at Google are what's keeping me from drowning. -- Grant Edwards grant.b.edwardsYow! Gee, I feel kind of at LIGHT in the head now, gmail.comknowing I can't make my satellite dish PAYMENTS! -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On 2013-05-29, Dan Stromberg drsali...@gmail.com wrote: And in case you still want a preprocessor for Python (you likely don't need one this time), here's an example of doing this using the venerable m4: https://pypi.python.org/pypi/red-black-tree-mod . Note the many comments added to keep line numbers consistent. I was wondering whether or not to mention m4. Since m4 is (in my mind) inextricably linked to RATFOR and sendmail config files I try to avoid thinking about it lest the flashbacks start again... -- Grant Edwards grant.b.edwardsYow! Hmmm ... a CRIPPLED at ACCOUNTANT with a FALAFEL gmail.comsandwich is HIT by a TROLLEY-CAR ... -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On Thu, May 30, 2013 at 12:55 AM, Grant Edwards invalid@invalid.invalid wrote: On 2013-05-29, Dan Stromberg drsali...@gmail.com wrote: And in case you still want a preprocessor for Python (you likely don't need one this time), here's an example of doing this using the venerable m4: https://pypi.python.org/pypi/red-black-tree-mod . Note the many comments added to keep line numbers consistent. I was wondering whether or not to mention m4. Since m4 is (in my mind) inextricably linked to RATFOR and sendmail config files I try to avoid thinking about it lest the flashbacks start again... It's not a bad tool. I used it as a sort of PHP preprocessor, because requirements at work had me wanting to have a source file defining a PHP class and having an autogenerated section in the middle of that class. PHP's 'include' directive doesn't work for that. Of course, had we been using a better language, that wouldn't have been an issue (and it stopped being an issue when we improved the design and stopped using that class system, too, though I retained the makefile directives about building .php.m4 - .php files). But still, GNU M4 is a decent piece of technology. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On 2013-05-29, Chris Angelico ros...@gmail.com wrote: On Thu, May 30, 2013 at 12:55 AM, Grant Edwards invalid@invalid.invalid wrote: On 2013-05-29, Dan Stromberg drsali...@gmail.com wrote: And in case you still want a preprocessor for Python (you likely don't need one this time), here's an example of doing this using the venerable m4: https://pypi.python.org/pypi/red-black-tree-mod . Note the many comments added to keep line numbers consistent. I was wondering whether or not to mention m4. Since m4 is (in my mind) inextricably linked to RATFOR and sendmail config files I try to avoid thinking about it lest the flashbacks start again... It's not a bad tool. I used it as a sort of PHP preprocessor, [...] But still, GNU M4 is a decent piece of technology. I didn't mean to disparage m4 -- it always seemed well thought out and useful. It just happens to be associated with unpleasant things for me. [And it didn't really seem like a good option for the OP's problem.] Still, if one really did want a preprocessor for Python programs, m4 would be the first thing I'd look at. -- Grant Edwards grant.b.edwardsYow! I wonder if I ought at to tell them about my gmail.comPREVIOUS LIFE as a COMPLETE STRANGER? -- http://mail.python.org/mailman/listinfo/python-list
Python #ifdef
Are there Python 'preprocessor directives'? I'd like to have something like '#ifdef' to mix code from Python 2 and 3 in a single file. Is that possible? How? -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
No On May 28, 2013 3:48 PM, Carlos Nepomuceno carlosnepomuc...@outlook.com wrote: Are there Python 'preprocessor directives'? I'd like to have something like '#ifdef' to mix code from Python 2 and 3 in a single file. Is that possible? How? -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On 05/28/2013 03:46 PM, Carlos Nepomuceno wrote: Are there Python 'preprocessor directives'? Python doesn't define a preprocessor, and CPYthon doesn't implement one. Nothing to stop you from doing so, however. I'd like to have something like '#ifdef' to mix code from Python 2 and 3 in a single file. Is that possible? How? It's quite possible that you don't need a preprocessor do what you want, since Python does much less compile-time checking than C. Also, it's possible to store function objects and module objects in variables, and thus to hide many things from the body of the code. One biggie is print, since that's a reserved word (and a statement) in Python 2.x. But if you're using 2.7 you can use from __future__ import print, or something like that, and just use 3.x function semantics. -- DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On 2013-05-28, Joel Goldstick joel.goldst...@gmail.com wrote: No Yes. More below. On May 28, 2013 3:48 PM, Carlos Nepomuceno carlosnepomuc...@outlook.com wrote: Are there Python 'preprocessor directives'? I'd like to have something like '#ifdef' to mix code from Python 2 and 3 in a single file. Is that possible? How? You need sys.version_info. For more, see http://python3porting.com/noconv.html -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
RE: Python #ifdef
Thank you! I made it run like the following. What do you think about that? IS there a better way? #The following runs on Python 2.7 sc3=''' # Python 3 def original(n): m = 0 for b in n.to_bytes(6, 'big'): m = 256*m + b return m ''' if sys.version_info[0] == 3: exec(sc3) -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On 2013-05-28, Carlos Nepomuceno carlosnepomuc...@outlook.com wrote: Thank you! I made it run like the following. What do you think about that? IS there a better way? #The following runs on Python 2.7 sc3=''' # Python 3 def original(n): ??? m = 0 ??? for b in n.to_bytes(6, 'big'): ??? m = 256*m + b ??? return m ''' if sys.version_info[0] == 3: ??? exec(sc3) You're trying to make this a lot harder than it really is: if sys.version_info[0] == 3: def original(n): m = 0 for b in n.to_bytes(6, 'big'): m = 256*m + b return m else: def original(n): something else? -- Grant Edwards grant.b.edwardsYow! Am I having fun yet? at gmail.com -- http://mail.python.org/mailman/listinfo/python-list
RE: Python #ifdef
On May 28, 2013 1:10 PM, Carlos Nepomuceno carlosnepomuc...@outlook.com wrote: Thank you! I made it run like the following. What do you think about that? IS there a better way? #The following runs on Python 2.7 sc3=''' # Python 3 def original(n): m = 0 for b in n.to_bytes(6, 'big'): m = 256*m + b return m ''' if sys.version_info[0] == 3: exec(sc3) -- No need for exec. if sys.version_info[0] = 3: def original(n) : ... -- http://mail.python.org/mailman/listinfo/python-list
RE: Python #ifdef
From: invalid@invalid.invalid Subject: Re: Python #ifdef [...] You're trying to make this a lot harder than it really is: if sys.version_info[0] == 3: def original(n): m = 0 for b in n.to_bytes(6, 'big'): m = 256*m + b return m else: def original(n): something else? -- Grant Edwards grant.b.edwards Yow! Am I having fun yet? at gmail.com Haha! That's it!!! Just realized how funny this can be: ;) ### never to be opened ### def pandoras_box(v): return v/0.0 if customer_didnt_pay(): pandoras_box() #lol -- http://mail.python.org/mailman/listinfo/python-list
RE: Python #ifdef
On 28 May 2013 21:26, Carlos Nepomuceno carlosnepomuc...@outlook.com wrote: Haha! That's it!!! Just realized how funny this can be: ;) ### never to be opened ### def pandoras_box(v): return v/0.0 if customer_didnt_pay(): pandoras_box() #lol 1/0 is, after print, my most common debug statement. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On 2013-05-28, Carlos Nepomuceno carlosnepomuc...@outlook.com wrote: [...] You're trying to make this a lot harder than it really is: if sys.version_info[0] == 3: def original(n): m = 0 for b in n.to_bytes(6, 'big'): m = 256*m + b return m else: def original(n): something else? Haha! That's it!!! Just realized how funny this can be: ;) Here's the important lesson from this thread: Instead of asking how do I write X in Python where yoy've assumed X is the solution to your problem, you're usually better off asking how to solve the underlying problem in a Pythonic way. IOW, instead of asking about a Python preprocessor (which you have assumed is the solution to the problem because that's how you would do it in C), ask about the actual problem (how to define a function differently depending on Python version). People on this list are very inventive and will expend a surprising amount of time to figure out often too-clever ways to do X because you asked how to do X -- even if doing X is a lousy way to solve your actual problem... When asking how do I solve a problem, it's OK to illustrate that question with an example X of how you would solve it in C or Java or Ruby or Perl or whatever, but remember 1) Not everybody here knows C or Java or Ruby or Perl or whatever, and the person who _does_ know everyting there is to know about solving some particular underlying problem isn't going to go learn a new language so that they can understand your example and figure out what you're trying to accomplish. 2) Programming languages differ. X may be the best way to solve the problem in one language, but it might be an awful way to do it in another language. -- Grant Edwards grant.b.edwardsYow! I'm ANN LANDERS!! at I can SHOPLIFT!! gmail.com -- http://mail.python.org/mailman/listinfo/python-list
RE: Python #ifdef
Date: Tue, 28 May 2013 21:34:36 +0100 Subject: RE: Python #ifdef From: fabiosantos...@gmail.com To: carlosnepomuc...@outlook.com CC: python-list@python.org On 28 May 2013 21:26, Carlos Nepomuceno carlosnepomuc...@outlook.commailto:carlosnepomuc...@outlook.com wrote: Haha! That's it!!! Just realized how funny this can be: ;) ### never to be opened ### def pandoras_box(v): return v/0.0 if customer_didnt_pay(): pandoras_box() #lol 1/0 is, after print, my most common debug statement. What's the best debugger for Python? Have you tried HAP[1]? [1] http://hapdebugger.sourceforge.net/ -- http://mail.python.org/mailman/listinfo/python-list
RE: Python #ifdef
From: invalid@invalid.invalid Subject: Re: Python #ifdef Date: Tue, 28 May 2013 20:42:34 + To: python-list@python.org [...] Here's the important lesson from this thread: Instead of asking how do I write X in Python where yoy've assumed X is the solution to your problem, you're usually better off asking how to solve the underlying problem in a Pythonic way. IOW, instead of asking about a Python preprocessor (which you have assumed is the solution to the problem because that's how you would do it in C), ask about the actual problem (how to define a function differently depending on Python version). People on this list are very inventive and will expend a surprising amount of time to figure out often too-clever ways to do X because you asked how to do X -- even if doing X is a lousy way to solve your actual problem... When asking how do I solve a problem, it's OK to illustrate that question with an example X of how you would solve it in C or Java or Ruby or Perl or whatever, but remember 1) Not everybody here knows C or Java or Ruby or Perl or whatever, and the person who _does_ know everyting there is to know about solving some particular underlying problem isn't going to go learn a new language so that they can understand your example and figure out what you're trying to accomplish. 2) Programming languages differ. X may be the best way to solve the problem in one language, but it might be an awful way to do it in another language. -- Grant Edwards grant.b.edwards Yow! I'm ANN LANDERS!! at I can SHOPLIFT!! gmail.com You're right! Sometimes I hate myself for doing exactly the opposite of what I would like to do! Unfortunately I can't change the thread subject. How do you have invalid@invalid.invalid instead of your email address? -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On 28/05/2013 20:46, Carlos Nepomuceno wrote: Are there Python 'preprocessor directives'? I'd like to have something like '#ifdef' to mix code from Python 2 and 3 in a single file. Is that possible? How? https://pypi.python.org/pypi/six/1.3.0 -- If you're using GoogleCrap™ please read this http://wiki.python.org/moin/GoogleGroupsPython. Mark Lawrence -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On Tue, May 28, 2013 at 6:18 PM, Mark Lawrence breamore...@yahoo.co.ukwrote: On 28/05/2013 20:46, Carlos Nepomuceno wrote: Are there Python 'preprocessor directives'? I'd like to have something like '#ifdef' to mix code from Python 2 and 3 in a single file. Is that possible? How? https://pypi.python.org/pypi/**six/1.3.0https://pypi.python.org/pypi/six/1.3.0 -- If you're using GoogleCrap™ please read this http://wiki.python.org/moin/* *GoogleGroupsPython http://wiki.python.org/moin/GoogleGroupsPython. Mark Lawrence -- http://mail.python.org/**mailman/listinfo/python-listhttp://mail.python.org/mailman/listinfo/python-list my original response was from cell phone. I just answered that you can't do ifdefs, implying that there is no preprocessor in python. I learned a lot of things I didn't know reading the thread, but I wonder if it is a good idea in general to try to write code like this. -- combined 2.x/3.x codebase can be a bear to maintain. I wouldn't do it unless there was some imposing reason that I must. Its not just print() -- that isn't bad, but changes in module names (urllib), arithmetic, and unicode especially make this idea in general, very tricky. Pity the next developer who needs to try to maintain it. So, maybe you CAN do it, but SHOULD you want to do it? -- Joel Goldstick http://joelgoldstick.com -- http://mail.python.org/mailman/listinfo/python-list
RE: Python #ifdef
Date: Tue, 28 May 2013 18:25:59 -0400 Subject: Re: Python #ifdef From: joel.goldst...@gmail.com To: breamore...@yahoo.co.uk CC: python-list@python.org [...] my original response was from cell phone. I just answered that you can't do ifdefs, implying that there is no preprocessor in python. I learned a lot of things I didn't know reading the thread, but I wonder if it is a good idea in general to try to write code like this. -- combined 2.x/3.x codebase can be a bear to maintain. I wouldn't do it unless there was some imposing reason that I must. Its not just print() -- that isn't bad, but changes in module names (urllib), arithmetic, and unicode especially make this idea in general, very tricky. Pity the next developer who needs to try to maintain it. So, maybe you CAN do it, but SHOULD you want to do it? -- Joel Goldstick http://joelgoldstick.com Thanks Joel! In this case I think it does because I would like to have the same short benchmarking script to be runnable by Python 2 and Python 3. The only piece of code that doesn't run on Python 2 is a to_bytes() single call. So it's not a huge maintenance load. ;) I didn't try to write 'portable' code to Python 3 yet. What's the catch? -- http://mail.python.org/mailman/listinfo/python-list
RE: Python #ifdef
On 28 May 2013 21:53, Carlos Nepomuceno carlosnepomuc...@outlook.com wrote: Date: Tue, 28 May 2013 21:34:36 +0100 Subject: RE: Python #ifdef From: fabiosantos...@gmail.com To: carlosnepomuc...@outlook.com CC: python-list@python.org On 28 May 2013 21:26, Carlos Nepomuceno carlosnepomuc...@outlook.commailto:carlosnepomuc...@outlook.com wrote: Haha! That's it!!! Just realized how funny this can be: ;) ### never to be opened ### def pandoras_box(v): return v/0.0 if customer_didnt_pay(): pandoras_box() #lol 1/0 is, after print, my most common debug statement. What's the best debugger for Python? Have you tried HAP[1]? [1] http://hapdebugger.sourceforge.net/ Never saw that, but the remote debugging looks like it adds some flexibility. That said, I don't often use a debugger. When I do, it's pdb. Pdb is not bad at all, and it comes in the stdlib, which makes it readily available in a virtualenv. It's impractical to set more than a breakpoint, but then again I only use a breakpoint at a time. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
Carlos Nepomuceno於 2013年5月29日星期三UTC+8上午3時46分37秒寫道： Are there Python 'preprocessor directives'? I'd like to have something like '#ifdef' to mix code from Python 2 and 3 in a single file. Is that possible? How? Use execfile(filename) at the beginning to get what you want. The .pyc version is preferred. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
On 5/28/2013 6:25 PM, Joel Goldstick wrote: On Tue, May 28, 2013 at 6:18 PM, Mark Lawrence breamore...@yahoo.co.uk mailto:breamore...@yahoo.co.uk wrote: On 28/05/2013 20:46, Carlos Nepomuceno wrote: I'd like to have something like '#ifdef' to mix code from Python 2 and 3 in a single file. https://pypi.python.org/pypi/__six/1.3.0 https://pypi.python.org/pypi/six/1.3.0 my original response was from cell phone. I just answered that you can't do ifdefs, implying that there is no preprocessor in python. I learned a lot of things I didn't know reading the thread, but I wonder if it is a good idea in general to try to write code like this. -- combined 2.x/3.x codebase can be a bear to maintain. Many people have come to prefer a) a single 23 codebase over b) separate 2 and 3 codebases or c) a single 2 codebase repeatedly converted to a 3 codebase with 2to3. They use 2to3 once (well, a few times) to discover differences that need to be considered. For 2.7 and 3.x, the future imports are enough for some code. The six module handles harder cases. I wouldn't do it unless there was some imposing reason that I must. Its not just print() -- that isn't bad, but changes in module names (urllib), I believe six handles that arithmetic, and from __future__ import integer_division # spelling? handles the only change unicode Use unicode consistently and from __future__ import unicode_literals # spelling? or the re-addition u'' prefix do quite well. Otherwise, do not use things that evaporated, like apply() and classic classes. (Inherit from object if nothing else.) This is all hearsay coming from me ;-). Terry -- http://mail.python.org/mailman/listinfo/python-list
Supporting both 2.x and 3.x in one code base [was Re: Python #ifdef]
On Tue, 28 May 2013 18:25:59 -0400, Joel Goldstick wrote: I wonder if it is a good idea in general to try to write code like this. -- combined 2.x/3.x codebase can be a bear to maintain. Not so much a bear as a tiny little kitten. I wouldn't do it unless there was some imposing reason that I must. Its not just print() -- that isn't bad, but changes in module names (urllib), arithmetic, and unicode especially make this idea in general, very tricky. Pity the next developer who needs to try to maintain it. It's not that hard really. Well, like all things, it depends on the circumstances. If you're reliant on external modules, you *may* have a bad time if those modules are 2.x only or 3.x only, but the standard library and built-ins don't provide too much of a challenge. There's no doubt that supporting 2.x and 3.x in one code base is more difficult that just supporting one or the other, but the difficulty is much less than often supposed. Python 2.7, and to a lesser extent, 2.6, are designed to be as easy to port to 3.x as possible, which has the happy side-effect that they are also relatively easy to write code for them that will also run under 3.x. Many of the differences can be eliminated with a few __future__ imports: from __future__ import division, print_function Differences in behaviour of the built-ins can be eliminated: from future_builtins import * Built-ins such as reduce and cmp that have been moved, or eliminated, can easily be restored: if sys.version = '3': from functools import reduce Or if you prefer a Better To Ask Forgiveness Than Permission approach: try: reduce except NameError: from functools import reduce Name changes of modules are easy to deal with: try: import configparser except ImportError: import ConfigParser as configparser The most difficult difference is the difference between strings in 2.x and 3.x, but if you drop support for Python 3.1 and 3.2, you can write code that works in both 2.7 and 3.3 by using the u syntax. Or just use ASCII literals, which work perfectly in both. There are really only a very few things that cannot be shared between 2.x and 3.x: syntactical features that are only supported by 3.x. So if you're planning on writing code that runs in both 2.x and 3.x, you need to eschew the 3-only features like keyword-only function arguments and function annotations. But that's no different than writing code to support *any* two versions that don't have identical syntax. E.g. 2.4 and 2.5: 2.5 supports ternary if, `a if condition else b`, while 2.4 does not, so if you need to support both, you can't use ternary if. Nearly all the code I write is for 2.4 or better, and I can assure you that the hardest part is supporting 2.4. Adding 3.x doesn't make it much harder. (My hat goes off to those supporting 2.3 through 3.3 in one code base. That is, frankly, astonishing.) Nobody *likes* to have to support really old versions missing the cool syntax that you want to use, but nobody says that you should even try. 3.x doesn't change that. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Python #ifdef
Here're slides from a presentation about writing code that runs on 2.x and 3.x: http://stromberg.dnsalias.org/~dstromberg/Intro-to-Python/ And in case you still want a preprocessor for Python (you likely don't need one this time), here's an example of doing this using the venerable m4: https://pypi.python.org/pypi/red-black-tree-mod . Note the many comments added to keep line numbers consistent. Sent from my android phone. On May 28, 2013 12:47 PM, Carlos Nepomuceno carlosnepomuc...@outlook.com wrote: Are there Python 'preprocessor directives'? I'd like to have something like '#ifdef' to mix code from Python 2 and 3 in a single file. Is that possible? How? -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
