8 Responses to “Collecting Python insights”

1. JB Says:
   July 3rd, 2008 at 9:05 pm

   xrange uses less memory, but it is slightly slower, as it needs to generate each value on demand.

   Just sayin’.

2. Mahadevan R Says:
   July 4th, 2008 at 7:40 am

   In RandomChunker.chunk(), instead of “return ret”, do “yield ret”. Then, you can:

   for chunk in rc.chunk():
   print chunk

   Cheers,
   -Mahadevan.

3. eliben Says:
   July 4th, 2008 at 8:21 am

   JB:

   As this benchmark demonstrates, you are quite wrong. xrange is faster (tried for both large and small LISTSIZE):

   import timeit
   
   setup = “”"
   LISTSIZE = 10
   “”"
   
   s1 = “”"
   k = 0
   for i in range(LISTSIZE): k += i
   “”"
   
   s2 = “”"
   k = 0
   for i in xrange(LISTSIZE): k += i
   “”"
   
   N = 50000
   print “range on integer”, timeit.Timer(stmt=s1, setup=setup).timeit(N)
   print “xrange on integer”, timeit.Timer(stmt=s2, setup=setup).timeit(N)
   

4. eliben Says:
   July 4th, 2008 at 8:21 am

   Mahadevan R:

   The “insights” supposes RandomChunk already exists and can’t be modified.

5. alain Says:
   July 4th, 2008 at 9:35 am

   Python doesn’t have a reverse builtin but it has a reversed builtin:
   for char in reversed(”hello world”):
   print char

6. Screwtape Says:
   July 4th, 2008 at 2:45 pm

   The example for ‘Dynamic code evaluation’ is a good example of how to use exec, but a bad example of when exec is appropriate.The following code is a much nicer way of achieving the same thing, because it doesn’t involve exec and hence you never have to worry about people feeding it malicious strings:

   def make_packet_extract(a, b):
   ____def foo(packet):
   ________return ord(packet[a]) + 256 * ord(packet[b])
   ____return foo

   (apologies for the underscores, <pre> didn’t seem to want to do its thing)

   A better example for exec might be something where you have to change the actual structure of the method you’re building rather than just values within it - changing ‘and’ to ‘or’ or similar.

7. Ivan Says:
   July 31st, 2008 at 8:49 am

   Function reverse won’t work for UTF8 strings

8. Pablo Says:
   August 2nd, 2008 at 11:09 am

   defaultdict(int) is faster than defaultdict(lambda: 0)

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