Re: ctypes - python2.7.3 vs python3.2.3

[Jan Kuiken]

On 8/28/12 23:51 , John Gordon wrote:

In <18eb8025-7545-4d10-9e76-2e41deaad...@googlegroups.com> Rolf 
 writes:


uint32_t myfunction (char ** _mydata)
{
char mydata[16];



strcpy(mydata, "Hello Dude!");



*_mydata = mydata;



return 0;
}


mydata is an auto variable, which goes out of scope when myfunction()
exits.  *_mydata ends up pointing to garbage.



I'm not completely sure, but i think this can be solved by using:

static char mydata[16];

(Btw.: I don't know why you use char ** _mydata, i would use
   char * _mydata, but then again, i'm not very familiar with
   ctypes)

Jan Kuiken

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Re: Objects in Python

[Jan Kuiken]

On 8/23/12 20:17 , Ian Kelly wrote:

...


Well, there you go. There *is* something wrong with having six variables
called 'q'.



Sometimes you don't want only six variables called 'q' but a hundred
of them :-)

   def fac(q):
   if q < 1 :
   return 1
   else:
   return q * fac(q-1)

   print(fac(100))



That's only one variable called 'q', instantiated 100 times simultaneously.


Bare with me, i come from a C world, and think of each variable,
whatever its name or scope, as a piece of memory and therefore
different.
btw. I like the idea of simultaneously instantiation :-)

Jan Kuiken
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Re: Objects in Python

[Jan Kuiken]

On 8/23/12 06:11 , Steven D'Aprano wrote:


2) Related to the above, you can infinitely nest scopes. There's nothing
wrong with having six variables called 'q'; you always use the innermost
one. Yes, this can hurt readability


Well, there you go. There *is* something wrong with having six variables
called 'q'.


Sometimes you don't want only six variables called 'q' but a hundred
of them :-)

  def fac(q):
  if q < 1 :
  return 1
  else:
          return q * fac(q-1)

  print(fac(100))


Jan Kuiken

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Re: Help doing it the "python way"

[Jan Kuiken]

On 5/24/12 22:22 , Scott Siegler wrote:


I am an experienced programmer but a beginner to python.  As such, I can figure out a way 
to code most algorithms using more "C" style syntax.

I am doing something now that I am sure is a more python way but i can't quite 
get it right.  I was hoping someone might help.

So I have a list of grid coordinates (x, y).  From that list, I want to create 
a new list that for each coordinate, I add the coordinate just above and just 
below (x,y+1) and (x,y-1)

right now I am using a for loop to go through all the coordinates and then 
separate append statements to add the top and bottom.

is there a way to do something like: [(x,y-1), (x,y+1) for zzz in coord_list] 
or something along those lines?


If you have lot's of numerical data you can use the NumPy module 
(http://numpy.scipy.org/), your problem would reduce to something like 
this (copied from an IPython shell, could be shorter)


Regards,
Jan Kuiken


In [1]: first_list = np.arange(0, 10).reshape((5,2))

In [2]: above = np.array([0,-1])

In [3]: below = np.array([0,+1])

In [4]: N,d = first_list.shape

In [5]: second_list = np.empty((N*2,d))

In [6]: second_list[0::2] = first_list + above

In [7]: second_list[1::2] = first_list + below

In [8]: second_list
Out[8]:
array([[  0.,   0.],
   [  0.,   2.],
   [  2.,   2.],
   [  2.,   4.],
   [  4.,   4.],
   [  4.,   6.],
   [  6.,   6.],
   [  6.,   8.],
   [  8.,   8.],
   [  8.,  10.]])

In [9]: first_list
Out[9]:
array([[0, 1],
   [2, 3],
   [4, 5],
   [6, 7],
   [8, 9]])
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Re: functions which take functions

[Jan Kuiken]

On 4/9/12 20:57 , Kiuhnm wrote:


Do you have some real or realistic (but easy and self-contained)
examples when you had to define a (multi-statement) function and pass it
to another function?


I don't use it daily but the first argument of list.sort, i.e. the
compare function springs to mind.

Jan Kuiken


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