On 2007-10-20, James Stroud <[EMAIL PROTECTED]> wrote: ><commentary>The long of it is that there are deep computer-science > issues that distinguish the two and the differences become more > important the more you know (presumably). However, I have been > programming this language for 5 years, and I still can't figure out the > necessity for having both. I have heard all of the arguments, however > but none are terribly pursuasive.</commentary>
The quick answer is that tuples can be indexes into directories while lists cannot. This doesn't seem like that big of a deal until you realize it allows you to group related but distict bits of data together to form an index while retaining their individual identity. A simplistic example would be if you had a map with x,y coordinates and you wanted to place items on that map at their location. [EMAIL PROTECTED]:~} python Python 2.4.4 (#2, Aug 16 2007, 02:03:40) [GCC 4.1.3 20070812 (prerelease) (Debian 4.1.2-15)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> x = 1 >>> y = 1 >>> coord = (x, y) >>> map = {} >>> map[coord] = "Something at x%s, y%s" % coord >>> map {(1, 1): 'Something at x1, y1'} >>> map[(1,1)] 'Something at x1, y1' >>> if map.has_key(coord): ... print "Found it!" ... >>> if map.has_key((1,1)): ... print "Found it!" ... Found it! >>> for loc in map: ... print "X: %s, Y: %s - %s" % (loc[0], loc[1], map[loc]) ... X: 1, Y: 1 - Something at x1, y1 The lists cannot be indexes to directories because they are mutable. [1. 1] might not be [1, 1] the next time you look for it. (1, 1) always will. -- Steve C. Lamb | But who decides what they dream? PGP Key: 1FC01004 | And dream I do... -------------------------------+--------------------------------------------- -- http://mail.python.org/mailman/listinfo/python-list