Re: C pointers/Python
len is a built-in function in Python, so you probably don't want to use it as a variable name. What is this C code actually trying to do? Don't try to transliterate it; instead, read up on how lists and slicing work, and rewrite it in Python starting from a higher level of abstraction. One hint- you can copy the same datum many times without a while loop... # reassign sub-list interval [i, j-1] buffer[i:j] = [data] * (j-i) # reassign the entire list buffer[:] = [data] * len(buffer) -- http://mail.python.org/mailman/listinfo/python-list
Re: C pointers/Python
On 21 Mar 2005 19:32:20 -0800, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Can i do something like this? if code == CODE1: data = 0x0 While True: len = len - 1 if len == -1: break buffer = data Do i need to initialze the buffer? Please, forget everything you know about memory, pointers, and C idiom. Also, considering doing the python tutorial. There is one provided here: http://python.org/doc/tut Basically, you're not approaching this in a python-like way, and thus what should be a single line (i.e. 'return data') you're trying to turn into a painful process of copying data from one memory location to another. This is acceptable in the C world, and not appropriate in the python world. I would suggest you define your problem in broader terms (i.e. I am trying to interpret data that is coming over a socket, my packet structure looks like this ..., how do I marshall dispatch that to callbacks so I can talk the protocol properly? Here is a link to the working C code http://...;) and there is a large group of wonderful people here that would love to show you the pythonic way of achieving your goal. -- Stephen Thorne -- http://mail.python.org/mailman/listinfo/python-list
Re: C pointers/Python
On 21 Mar 2005 15:52:44 -0800, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
Hello,
I am trying to convert some C code into python.
Here's the C code...
typedef enum {
CODE1 = 0x1,
CODE2 = 0x2
} CODE
testit(unsigned char *buffer,
unsigned long length,
CODE code)
{
unsigned long data
switch (code)
{
case CODE1:
while(len--)
{
*buffer++ = (unsigned long)data++
}
break
CODE1 = 1
CODE2 = 2
def testit(code):
data = 'somedata'
if code == CODE1:
return data
In C, you pass a memory location to copy the result into. In Python,
we return the result as an object.
As for pointers, we don't need them.
--
Stephen Thorne
Development Engineer, NetBoxBlue.com
--
http://mail.python.org/mailman/listinfo/python-list
Re: C pointers/Python
you never deal directly with pointers in python. in your case, you need to pass a mutable object as your 'buffer' argument and perform operations on it such that 'buffer==data'. (for example, you could use a list here.) def testit( buffer ): for i in range( len ): buffer[A+i]=data[B+i] for some constants A,B -- http://mail.python.org/mailman/listinfo/python-list
Re: C pointers/Python
On 21 Mar 2005 17:16:18 -0800, integer [EMAIL PROTECTED] wrote: you never deal directly with pointers in python. in your case, you need to pass a mutable object as your 'buffer' argument and perform operations on it such that 'buffer==data'. (for example, you could use a list here.) def testit( buffer ): for i in range( len ): buffer[A+i]=data[B+i] for some constants A,B That's unpythonic. The correct solution is to return the result. Anything else is trying to squeeze a C idiom into python for no gain. -- Stephen Thorne Development Engineer, NetBoxBlue.com -- http://mail.python.org/mailman/listinfo/python-list
Re: C pointers/Python
agreed. you might say i was trying to translate his C code word for word, rather than properly pythonizing the entire chunk of code as a whole. -- http://mail.python.org/mailman/listinfo/python-list
Re: C pointers/Python
Can i do something like this? if code == CODE1: data = 0x0 While True: len = len - 1 if len == -1: break buffer = data Do i need to initialze the buffer? -Thanks, Joe -- http://mail.python.org/mailman/listinfo/python-list
Re: C pointers/Python
Can i do something like this? if code == CODE1: data = 0x0 While True: len = len - 1 if len == -1: break buffer = data certainly not! there are many things wrong with that. first of all, as was pointed out already: this is highly un-pythonic. secondly, its completely wrong. if you bind 'buffer' to another object, then you have no chance of modifying its original contents. thats why i stated in my previous post that IF you insist on persuing the un-pythonic path then your function argument 'buffer' _must_ be a mutable object which you must operate on through its methods, but you CANNOT modify it with: buffer=data. doing that will only re-bind 'buffer', it will never change anything outside the function. -- http://mail.python.org/mailman/listinfo/python-list
