Javier Bezos wrote:
> "Jacob Lee" <[EMAIL PROTECTED]> escribió en el mensaje
> > satisfy some handy properties, the first of which being:
> > l[:n] + l[n:] = l
>
> I don't think l[:5] + l[5:] = l is a handy property
> and to me is clearly counterintuitive. Further,
It can be quite useful for inserting something into a list (or string),
after finding the position where you wish to insert it.
improvedList = l[:n] + [new stuff] + l[n:]
I'm very fond of Python's slice indexing - it makes a number of things
fairly easy, for example:
myList[:N] # first N items
myList[-N:] # last N items
myList[start:start+N] # N items, from start position
# chunk a list into smaller lists (or strings into smaller strings)
# (thanks to Thorsten Kampe for the original example)
def chunky(sequence, N):
for i in range(len(sequence)/N + bool(len(sequence) % N)):
print sequence[i*N:(i+1)*N] # no off-by-one errors here :-)
myList = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
N = 3
chunky(myList, N)
which returns:
[0, 1, 2]
[3, 4, 5]
[6, 7, 8]
[9]
Note you can leave out the bool part if you don't want that partial
chunk at the end.
I vaguely remember hearing at one stage that the
sequence[position:position+length] notation is also potentially useful
for indexing into large strings or buffers.
Alex Martelli stated back in 2001, when this issue was previously
discussed:
> it IS just an extension of what Koenig
> explains in his book "C Traps and Pitfalls", about how
> always using half-open ranges helps avoid off-by-one
> errors that otherwise tend to plague programs.
Regards, Myles.
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