finding byte order
Hello, I am using a program that has to read binary data from files coming from different machines. The file are always written with big endian. I am using the struct module to read the data and it is fine because I can specify in the format if the data are to be read with big or small endian convention. I would like to use the array module instead of struct because it is suppose to be faster for big arrays. However, this module does not provide a format specifier to say if the data are writtent with big or small endian. The result is that it works on big-endian machine and not on small-endian machine. I would like to have a test to tell me if the current machine is using big or small endian, this way I could use the array module in the first case and the *slower* struct module on the second. I looked but did not find. Is there a python function to know that? Thanks! -- http://mail.python.org/mailman/listinfo/python-list
getting env variable from bourne shell script
Hello, I have file called PARAMETRES that is used in bourne shell script to define variable. In order to do so I put a ". PARAMETRES" line and the script has acces to all the variable defined in the PARAMETRES file. Now, I would like to be able to get the same thing in python. I googled and played with os.system to try to come up with something but no success so far. I also tryed exec but it doesn't work becaus a lot of string variable difined in the PARAMETRES file do not have the ' sign needed in python string. for example. Let's say I have a file PARAMETRES containing TOTO=whatever, I would like to have a command to read that file and have the variable TOTO='whatever' in python. Thanks for any help. Sébastien -- http://mail.python.org/mailman/listinfo/python-list
Re: finding byte order
Scott David Daniels wrote:
> biner wrote:
> > I am using a program that has to read binary data from files
coming
> > from different machines. The file are always written with big
endian.
>
> Diez B. Roggisch wrote:
> [Scott David Daniels wrote]
> >>How about sys.byteorder?
> > This doesn't help, as he wants to read files from varying endianess
- what
> > the _current_ endianess is doesn't matter here.
>
> But, in fact, he says the files are always big endian. So, code like
> the following should address his problem. Note I use type 'h' as an
> example so I can easily read samples.
>
> import sys, array
> f =open('huge.dat')
> v = array.array('h') # Or whatever data type
> v.fromfile(f, 4096)
> f.close()
> if sys.byteorder == 'little':
> v.byteswap()
>
> --Scott David Daniels
> [EMAIL PROTECTED]
This seems to do the what I want. I did not know about array.byteswap
and sys.byteorder.
Thanks for taking the time to answer my silly question.
Ciao!
--
http://mail.python.org/mailman/listinfo/python-list
why is this not working? (nested scope question)
I have a problem understanding the scope of variable in nested function. I think I got it nailed to the following example copied from Learning Python 2nd edition page 205. Here is the code. def f1() : x=88 f2() def f2() : print 'x=',x f1() that returns an error saying that "NameError: global name 'x' is not defined". I expected f2 to "see" the value of x defined in f1 since it is nested at runtime. My reading of the book comforted me in this. What am I missing? Shouldn't the E of the LEGB rule take care of that. BTW, I am running this on python 2.3. Thanks. Sébastien. -- http://mail.python.org/mailman/listinfo/python-list
Re: why is this not working? (nested scope question)
Thanks for the answers. I do understand (and verified) that if I define f2 within f1, it works as expected. But in the "learning pyton 2nd edition" at page 205 it is said that "Programs are much simpler if you do not nest defs within defs" (juste before the code mentioned in my initial message). In a way, I though the local variables of f1 would in a way add to the global variable of f2 (because f1 called f2) and that f2 would look in the global variables when it could not find a variable locally (following the LEGB rule). Still the code I put is presented in the book and it does not work for me. I googled for errata regarding that code but did not find any. Sébastien. -- http://mail.python.org/mailman/listinfo/python-list
Re: why is this not working? (nested scope question)
> Actually, the code in the book is: > > def f1(): > x = 88 > f2(x) > > def f2(x): > print x > > f1() > > which makes all the difference in the world. Not to mention that this > particular section of the book is giving an example of how to write the > code *without* using nested functions. Ouch! You got me there, I did not copy the code properly. Now I feel stupid. Thanks for the enlightment. I think I am starting to get it. Sébastien. -- http://mail.python.org/mailman/listinfo/python-list
