[Tutor] getopts question
Hello List Members, I am working on a simple program and would like to know the best way to approach this. Using getops I am parsing the argv array to grab command line options; from the command line the user can specify either a filename or a directory (but not both). Is there an eloquent way with getopts to do an either/or scenario without resorting to multiple tests to see which variable is set using if then statements? Thanks in advance ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] hashlib weirdness
Here's one that has me stumped.
I am writing a forensic analysis tool that takes either a file or a directory
as input, then calculates a hash digest based on the contents of each file.
I have created an instance of the hashlib class:
m = hashlib.md5()
I then load in a file in binary mode:
f = open("c:\python25\python.exe", "rb")
According to the docs, the hashlib update function will update the hash object
with the string arg. So:
m.update(f.read())
m.hexdigest()
The md5 hash is not correct for the file.
However, this works:
f.seek(0)
hashlib.md5(f.read()).hexdigest()
Why the difference I wonder?
Thanks in advance.
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Re: [Tutor] getopts question
Yeah I figured that. I am trying to find a way to have the program detect if the user input is a file or directory, which is easy enough with os.path. However, os.path makes no distinction between a regular file and a mask, eg filename.txt or *.txt. I guess I'll have to have a second set of tests to see if the filename contains any wildcards..? -Original Message- From: Kent Johnson >I'm not really sure what you are looking for here. If you use two options, you >will have to test to see which option is set. You could use one option, then >you will have to test to see if the value is a file or a directory. > >Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] os.path.isfile and isdir
It looks like both os.path.isfile and os.path.isdir evaluate to False for a wildcard, so that makes it a bit easier to deal with a mask. Thanks to everyone for the suggestions. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Communication between classes
Hi again, I am still in the process of learning OOP concepts and reasons why classes should be used instead of functions etc. One thing that is not apparent to me is the best way for classes to communicate with each other. For example, I have created an Args class that sets a variety of internal variables (__filename, __outputdir etc) by parsing the argv array from th command line. What would be the preferred mechanism for returning or passing along those variables to another class? Maybe by a function method that returns all of those variables? ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Communication between classes
That makes sense, thank you for the detailed explanation Andrei. For this simple project I am working on, it looks like the most direct route would be to use functions and only develop classes for the portions of the program that can be reused. Is it safe to say that classes are only useful for instances where reuse is a key consideration? From my very limited perspective, it seems that classes are in most cases overkill for simple tasks (such as reading the command line then calculating a hash/checksum to verify integrity). Thanks again for your very descriptive answer. -Original Message- From: Andrei Hi Greg, > >Greg Perry wrote: > I am still in the process of learning OOP concepts and > > reasons why classes should be used instead of functions etc. > > One thing that is not apparent to me is the best way for > > classes to communicate with each other. For example, > >Good question. Unfortunately there's no general rule that you can apply >and end up with an undisputably perfect solution. > >Classes should communicate on a need-to-know basis. Take for example a >RSS feed reader application. You may have a class representing a feed >and a class representing a post. The feed will know what posts it >contains, but the post probably won't know what feed it comes from. The >interface would display a list of feeds (without knowing their >contents), a list of posts within a feed (this needs to know both feed >and feed contents) and the contents of a single post (knows only about >an individual post). > > > I have created an Args class that sets a variety of internal > > variables (__filename, __outputdir etc) by parsing the argv > >Be careful with classes that simply act as a container for what are in >fact global variables. A class should do one thing only (of course what >you accept as 'one thing' is open for debate) and encapsulate all that's >necessary for that particular thing. Make sure you're not >overcomplicating your solution by making classes where they're not >really necessary. > > > array from th command line. What would be the preferred > > mechanism for returning or passing along those variables > >In some cases only some parts of the information contained in class A >are relevant to class B - you should pass only that particular >information, e.g. in the constructor or by setting a property of B. In >your example, if you have a Reader class that is interested in the >filename, you would not pass the whole Args object to it - only the >filename, like this: > > myreader = Reader(Args.FileName) > > > to another class? Maybe by a function method that returns > > all of those variables? > >Use properties if you need getter/setter methods or simple attributes >otherwise. In your case, I would not make __filename etc. 'private' >(that's what the double underscore suggests), then write a getter method >for it - just call it FileName and be done with it. Python idiom here is >more flexible than other languages. > >-- >Yours, > >Andrei > >= >Mail address in header catches spam. Real contact info: >''.join([''.join(s) for s in zip( >"[EMAIL PROTECTED] pmfe!Pes ontuei ulcpss edtels,s hr' one oC.", >"rjc5wndon.Sa-re laed o s npbi ot.Ira h it oteesn edt C")]) > >___ >Tutor maillist - Tutor@python.org >http://mail.python.org/mailman/listinfo/tutor > > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] hashlib weirdness
Thanks Terry, others have pointed out the same thing. The stock Python 2.5
interpreter functions properly; my issue seems to be with the IDE I am using,
that is where I've been able to nail down the problem so far.
-Original Message-
From: Terry Carroll
On 30 Mar 2007, Greg Perry wrote:
>
>> Here's one that has me stumped.
>
> I am writing a forensic analysis tool that takes either a file or a
> directory as input, then calculates a hash digest based on the contents
> of each file.
>
> I have created an instance of the hashlib class:
>
> m = hashlib.md5()
>
> I then load in a file in binary mode:
>
> f = open("c:\python25\python.exe", "rb")
>
> According to the docs, the hashlib update function will update the hash
> object with the string arg. So:
>
> m.update(f.read())
> m.hexdigest()
>
> The md5 hash is not correct for the file.
>
>Odd. It's correct for me:
>
>In Python:
>
>>>> import hashlib
>>> m = hashlib.md5()
>>> f = open("c:\python25\python.exe", "rb")
>>> m.update(f.read())
>>> m.hexdigest()
>'7e7c8ae25d268636a3794f16c0c21d7c'
>
>Now, check against the md5 as calculated by the md5sum utility:
>
>>md5sum c:\Python25\python.exe
>\7e7c8ae25d268636a3794f16c0c21d7c *c:\\Python25\\python.exe
>
>
>> f.seek(0)
> hashlib.md5(f.read()).hexdigest()
>
>No difference here:
>
>>>> f.close()
>>> f = open("c:\python25\python.exe", "rb")
>>> hashlib.md5(f.read()).hexdigest()
>'7e7c8ae25d268636a3794f16c0c21d7c'
>
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>Tutor maillist - Tutor@python.org
>http://mail.python.org/mailman/listinfo/tutor
>
>
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Re: [Tutor] Movies from jpg files
Maybe PyMedia is what you are looking for: http://www.pymedia.org It's a Python library based on FFmpeg, which is a program that can encode and decode many different video streams. FFmpeg can also create an mpeg from a collection of jpeg images, read section 1.2 of the FFmpeg FAQ which demonstrates making a mpeg from a sequence of jpeg images: http://ffmpeg.mplayerhq.hu/faq.html Subject: [Tutor] Movies from jpg files To: tutor@python.org Dear All, > >I have found a fine Axis 2100 webcamera on my shelf, that was out of >usage, >It uploads jpg images every minutes to an ftp server now. >I would like to build up a movie from the pictures for easier review. >I don't know which movie format can be built up easier, >.jpeg, quicktime .mov, .wmv, .avi or anything else. >It would be fine to use a format that has compression advantage compared >the raw >volume of jpg files. It could be possible as the camera placed statically >so the images >are very similar. > >May you recommend me which format could be used ? >May you recommend anything to build them easy ? > > >Yours sincerely, >__ >János Juhász > >___ >Tutor maillist - Tutor@python.org >http://mail.python.org/mailman/listinfo/tutor > > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Movies from jpg files
Indeed ;) >Python is Cool :) ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] please help me
Let no good deed go unpunished! -Original Message- From: Daniel Yoo Date: Friday, Apr 13, 2007 8:24 pm Subject: Re: [Tutor] please help me > If this is homework, please tell your teacher I helped - I need the > extra credit. > >Please avoid giving homework answers like this. Rather than actually help >the person, it can do harm, because it encourages a lazy attitude toward >solving problems. ___ Tutor maillist - [EMAIL PROTECTED] http://mail.python.org/mailman/listinfo/tutor
