On Tue, 15 Jan 2008 11:33:36 +0100, Helmut Jarausch wrote:
> Hi,
>
> I'm looking for an elegant solution of the following tiny but common
> problem.
>
> I have a list of tuples (Unique_ID,Date) both of which are strings. I
> want to delete the tuple (element) with a given Unique_ID, but I don't
> known the corresponding Date.
>
> My straight forward solution is a bit lengthy, e.g.
>
> L=[("a","070501"),("b","080115"),("c","071231")] pos=-1
> found=-1
> for (Key,Date) in L :
> pos+= 1
> if Key == "b" :
> found= pos
> break
>
> if found >= 0 :
> del L[found]
>
> print L
>
> Most probably there are much more elegant solutions. Unfortunately, the
> index-list-method doesn't take an additional function argument for the
> comparisons.
Your code mixes two distinct steps into one, and therefore becomes a
little messy. I suggest you change your problem to the two step problem
(1) find an item with the given key; and (2) delete it.
Here's a solution to the first part:
def find_by_key(L, key, where=0):
"""Search the 'where'th position of elements of L."""
for i, x in enumerate(L):
if x[where] == key:
return i
return -1 # or raise an exception
And the second:
pos = find_by_key(L, 'b')
if pos != -1:
del L[pos]
This too could be made into a function, if necessarily.
How else could we solve this problem?
class Tester(object):
def __init__(self, key, where=0):
self.key = key
self.where = where
def __eq__(self, other):
return other[self.where] == self.key
L = [("a", "070501"), ("b", "080115"), ("c", "071231")]
L.index(Tester("c"))
But beware, this technique might not generalize to arbitrary elements in
the list L. It should work if the elements are tuples, but may not work
if they are a custom class.
--
Steven
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