Re: [Tutor] Processing unix style timestamp
Ravi Kondamuru wrote:
Hi,
I have a log file that prints the date and time in the following format:
Mon Feb 11 01:34:52 CST 2008
I am expecting multiple timezone entries (eg: PST, PDT and GMT) on the
system running in America/Los Angeles time zone.
I am looking for a way to internally store all the different timezone
entries in GMT.
I looked at datetime, but it seems slightly complex to work with non GMT
timestamps.
Any pointers?
If you are not offended by a 3rd-party module, then the string parser
included in the egenix mxDateTime module[1] is hard to beat. You may
even have it installed already, as it appears to be a popular dependency
of other 3rd-party modules, especially db adapters.
In [1]: import mx.DateTime
In [2]: d = mx.DateTime.DateFrom('Mon Feb 11 01:34:52 CST 2008')
In [3]: d
Out[3]: mx.DateTime.DateTime object for '2008-02-11 07:34:52.00' at
b788d138
In [4]: d.strftime('%a %b %d %H:%M:%S %Y')
Out[4]: 'Mon Feb 11 07:34:52 2008'
In [5]: d = mx.DateTime.DateFrom('Mon Feb 11 01:34:52 EST 2008')
In [6]: d.strftime('%a %b %d %H:%M:%S %Y')
Out[6]: 'Mon Feb 11 06:34:52 2008'
In [7]: d = mx.DateTime.DateFrom('Mon Feb 11 01:34:52 UTC 2008')
In [8]: d.strftime('%a %b %d %H:%M:%S %Y')
Out[8]: 'Mon Feb 11 01:34:52 2008'
HTH,
Marty
[1] http://www.egenix.com/products/python/mxBase/mxDateTime/
thanks,
Ravi.
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Re: [Tutor] Const on Python
Andreas Kostyrka [EMAIL PROTECTED] wrote Yes, the problem is, that these guys are anyway forced to have Python/Erlang developers on board, because of external opensource components they need to maintain. And that one fact completely changes the economics and thereby renders the lead position non viable. The problem here is that C++ is a strong mismatch for the job at hand. With strong mismatch I mean hear at least a magnitude more costs. During initial development and during maintenance. I would be amazed at anuy project where a language made an order of magnitude difference. The difference in moving from assembler to VB is only about double (Thats the only case wehere I have hard experrience). The problem is as Fred Brooks stated in his essay No Silver Bullet that the real costs in development are the intengibles - the time spent thinking about theproblem/solution and dealing with people. They far outweigh the time actually writing code. The average project delivers around 20-100 lines of working code per day. But you can type that in mechanically in half an hour or less. The rest of the day is doing the stuff that really costs. Combined with the fact that the group cannot avoid learning Python andErlang, because external OSS projects used by them that they need to maintain and customize are written in Python Erlang. But this is the critical bt that was missing from the original problem statement. If they use these languages anyway then it makes sense to expand their code base. If these were niche languages on a dying legacy then it makes no sense to increase their use. But basically, your argument misses one important aspect: While most languages are equivalent in a theoretical sense ... Some languages can and do provide at least a magnitude of improvement compared to other languages. I do dispute that and would be interested in any objective figures that you have. All of the figures I've seen suggest the total project cost impact of lanmguage choice is rarely more than 10-20% of TCO Now add to the fact that software developement does not scale linearly, and the developer efficiency point becomes even more important. But as projects get bigger language choice becomes vanishingly small in the equation. Total developer cost in any large projerct rarely exceeds 10% and of that the language might make up 20% at most, so total impact of language reduces to around 1-2% of TCO. If, by using some higher language a problem becomes so easy to solve that a single developer can deal with it, instead of say a 4 man team,than this is a critical aspect. In that case I agree and at that small scale of project then language choice is still a valid argument. And for the kind of maintenance type feature fix we were discussing the project is quite small. (Different if the language choice requires a rewrite of the existing app of course!) It's kind like having a policy that all invoices must be in USD and are payed only in USD. Now two companies bid. I'm sorry, I think I missed the connection in the analogy. (Philosophically, that's not even that bad a comparison, as learning Python is a rather minor thing for a reasonable good developer. I totally agree, but unfortunately in the corporate world where I work there are relatively few good developers - typically one or two per team(around 6-10 people). Indeed only about half of our developers are formally trained to University Engineering/Computer Science type level. Many have craft certificvates from a trade school and (even if just psychologicalluy) learning a new language is a huge hurdle for them. They will insist on going ona weeks training course etc. So yes, most good developers can pick up Python in a couple of days from the web site, many corporate programmers balk at such an idea. (This is one area where a hobbyist turned pro is better than a journeyman programmer, the hobbyist is much more likely to learn new skills out of interests sake!) So no, I do not concur with you. I understand why it has some value, but you wouldn't argue that your company should use passenger cars to transport 100 tons of goods, just because all employee have a license to drive such, while truck drivers are slightly harder to come by, would you? No, but I might suggest hiring some trailers or using an external haulage company. It all depends on wheher its a one-off job or a new line of work that we need to build skills. So in this analogy we may need to buy a truck and start training a number of staff to drive it, but thats expensive so before doing so I'd look to see if it was one-off and at the other options. If in your example they need Python/Erlang anyway that completely changes the economics. Alan G. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] identifying the calling module/function
Hello Tutor! I am building a couple of scripts to manage a database for our company. The projects name is 'dgf'. As a lot of the functionality is used in more than one of these scripts, I moved this functionality to a module (dgf.py). It has several functions now. Question: Is there an easy way to determine inside dgf.py where the function call came from? dgf.py: def yetanotherfunction(): Edit Me! if function call came from script.py: ... Something like that? Regards -paul ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] identifying the calling module/function
[EMAIL PROTECTED] wrote: Hello Tutor! I am building a couple of scripts to manage a database for our company. The projects name is 'dgf'. As a lot of the functionality is used in more than one of these scripts, I moved this functionality to a module (dgf.py). It has several functions now. Question: Is there an easy way to determine inside dgf.py where the function call came from? Why do you need to do this? It sounds like a design change is needed. Anyway the answer to your question is yes. This recipe should point you in the right direction: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66062 Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Const on Python
Kent Johnson [EMAIL PROTECTED] wrote in (Jumping in against my better judgment :-) :-) Hmm...sure, programming is not about typing, it is about figuring out what to type. With Python the conceptual activity takes place at a higher level because - Python provides easy-to-use, high-level constructs like lists, dicts and first-order functions - Python doesn't require you to think about low-level details like const, private, getters and setters, braces, etc. Yes but thats not the bit that takes time in my experience its trying to understand the problem. What exactly am I trying to do here? Is it a suimulation exercise, a database problem? A real-time or networking issue? Should my solution include security protection? If so how much? Can I use a standard sort or do i need a custom algorithm? And if so what is it? Designing an algorithm takes far longer than converting it to code in any language. So Python speeds up the thinking part. It speeds up the thinking abouit code bit, it doesn't help much in the thining about the problem part. As far as the code, those 20-100 lines will do more if they are in Python than they will if they are in Java or C++. Absolutely, thats why I write in Python and let the developers do the Java stuff - life is too short! And thats why I am on a Python mailing list not a Java one :-) I don't see an order of magnitude difference between Python and Java And thats my point, particularly for bigger projects where the problem complexity completely dominates the code complexity. The coding time will derinitely improve and I suspect you could get as high as 4 or 5 times but I doubt if you'd ever really achieve an order of magnitude. have compared code samples, I have found Python code to be 20-60% the size of equivalent Java code. In the few cases I've measured its been about 30% less which nearly falls into your range. But the examples were very small - all less than 1000 lines of Java - about as much Java as I can bring myself to type! Alan G. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Creating a Python module to drive a robot
Hi all, I'd like to create a library of functions that would allow writing Python scripts that would control a Hemisson robots via a serial interface. I'll be using the pyserial module heavily, but I'm wondering what would be the best way to approach this . Should I create a Robot class and define everything as functions of the class, such as a function for setting wheel speed, turning, reading from sensors etc. Or is there some other way that would be easier for a user? The project is meant for students who would be using programming the robot as an Intro to programming, so it would be best if users don't need to understand the details of OOP (or similar concepts) to use the code quickly and reliably. Thanks, Basu ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Const on Python
Am Freitag, den 07.03.2008, 21:13 + schrieb Alan Gauld: Yes but thats not the bit that takes time in my experience its trying to understand the problem. What exactly am I trying to do here? Is it a suimulation exercise, a database problem? A real-time or networking issue? Should my solution include security protection? If so how much? Can I use a standard sort or do i need a custom algorithm? And if so what is it? Designing an algorithm takes far longer than converting it to code in any language. Right, but I've encountered it more than once in my professional life, that the C++ guys where still trying to implement a simple algorithm, while I was already finetuning a 2nd or 3rd generation of code. And while it's not always a magnitude, and it's hard to measure, the few times where I had to ability to compare (either because I was working parallel or was replacing a failed C++ project), a magnitude seems to describe the difference in development efficiency. And this incremental improvements is the usual way, because without a working prototype it's hard (and partially foolish) to decide which parts of the design need improvements. (Remember, Good-Enough is the relevant criteria when it comes to performance, so designing and implementating the best algorithm from scratch does not make sense (because often vastly simpler algorithms can provide the needed performance, and again, it's really hard to guess which parts will be critical for the performance) So Python speeds up the thinking part. It speeds up the thinking abouit code bit, it doesn't help much in the thining about the problem part. You are forgetting a critical part. When speaking about coding, I'm talking about writing the code, and getting it reasonable bugfree/usable. And that's where Python shines. As far as the code, those 20-100 lines will do more if they are in Python than they will if they are in Java or C++. Absolutely, thats why I write in Python and let the developers do the Java stuff - life is too short! And thats why I am on a Python mailing list not a Java one :-) I don't see an order of magnitude difference between Python and Java And thats my point, particularly for bigger projects where the problem complexity completely dominates the code complexity. The coding time will derinitely improve and I suspect you could get as high as 4 or 5 times but I doubt if you'd ever really achieve an order of magnitude. Actually, the project where I achieved over a magnitude speedup was highly complicated, involved partial reverse-engineering of binary formats, embedding Python in a C++ app, refactoring the C++ app to support multiple input handlers, doing a framework, optimizing, portability to all kind of old UNIX boxes (the app had designed minimum life cycle of 30 years), ... The C++ guys gave up in disgust after more than 9 months into the project. I had overtaken all their tries after one month. OTOH, if I'd compare me with the designed time for the project (which was 12 months), I have been only 2-3 times as fast as management had planned. In practice, the C++ guys had massive problems, and if their progress had been any measure, they would have taken at least 24-30 months getting the project going. I know it's unnice, because the project had not complete specifications (well, management claimed that it had all specs needed, as it happens the more important half of the specs needed to be reverse engineered. With data files in the MB range, manual decoding was not an workable solution. But the experimenting wasn't that bad with for me, while the C++ guy never reached the point where deciphering the semantic meaning of the data was relevant to them.) So I stand by the magnitude of developer efficiency difference. It's not there for every project, but OTOH there are other projects where you can get even more speedup. (Don't you have ever listened in on projects that are infrastructure building that is just, well, a nonissue in Python?) And btw, it's not just Python, it just happens to me my default language. Highlevel languages do pay, and it's starting to show slowly in the industry. (Well, 1-2 years ago, my CV was optimized to for non-Python experience. The last year, I've been usually able to pick Python contracts without much of troubles, so Python is growing in commercial settings.) have compared code samples, I have found Python code to be 20-60% the size of equivalent Java code. In the few cases I've measured its been about 30% less which nearly falls into your range. But the examples were very small - all less than 1000 lines of Java - about as much Java as I can bring myself to type! Well, Java is already a relative high-level language, it's basically safe, which helps debugging greatly, and is being made into something even more highlevel by all kinds of IDE wizards. I wouldn't expect a magnitude between Java/Python, just because Java is way nearer to Python
Re: [Tutor] Const on Python
Alan Gauld wrote: Absolutely. I totally agree that moving an organization to Python or similar modern language is a sensible move for many applications. Only where very high performance or scaleability are required would Python (or similar) be inappropriate and even in the largest organisations that is a minority case. And of course web services provide a glue that any language can utilise to remove most issues of integration between apps in different languages (which used to be a very valid concern). My only dispute is the wisdom of introducing foreign code into an existing app. Andreas has already said in fact the new languages are already supported so that makes the scenario valid also. Well, I guess it's about what you think a programmer is. I think if you are a true programmer you'll be good in ANY language (though you may have your preferences) and you'll be able to do 80% of your work in any language (and learn 80% of any language in a short time). So there would not really be such a problem with foreign code, the only issues I foresee are establishing proper coding rules for the company, that might take some time and produce some flaky code. As for integration between apps, if the languages are python and C/C++ it seems not to be a problem (never done it), there is : http://www.python.org/doc/ext/intro.html Ricardo ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Const on Python
On Mar 7, 2008, at 7:48 PM, Ricardo Aráoz wrote: Alan Gauld wrote: Well, I guess it's about what you think a programmer is. I think if you are a true programmer you'll be good in ANY language (though you may have your preferences) and you'll be able to do 80% of your work in any language (and learn 80% of any language in a short time). So there would not really be such a problem with foreign code, the only issues I foresee are establishing proper coding rules for the company, that might take some time and produce some flaky code. As for integration between apps, if the languages are python and C/C++ it seems not to be a problem (never done it), there is : http://www.python.org/doc/ext/intro.html It's easy to learn the basic features of a language and to use those, but developing fluency is much harder, and it takes a much longer time. - Jeff Younker - [EMAIL PROTECTED] - ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
