[Tutor] Finding the Index of a member of a Tuple

[Brian van den Broek]

bob said unto the world upon 11/01/06 10:47 PM:
> At 08:31 PM 1/11/2006, Steve Haley wrote:
> 
>>Hello everyone,
>>
>>I need to do something very simple but I'm having trouble finding 
>>the way to do it - at least easily.  I have created a tuple and now 
>>need to find the position of individual members of that 
>>tuple.  Specifically, the tuple is something like: words = ("you", 
>>"me", "us", "we", "and", "so", "forth") and I need to be able to 
>>name a member, for example, "us" and find what the position (index) 
>>of that word is in the tuple.
>>
>>I would have thought there would be a simple built in function for 
>>that but I just went through the built in functions in the Python 
>>Library Reference and I didn't find anything.  I could probably 
>>figure out how to write a while loop or something to do a sequential 
>>search until I found the right member but I really believe there 
>>must be an easier way and I'm just not seeing it.  You can probably 
>>tell I'm just learning Python so any help would be appreciated.
> 
> 
> Unfortunately there is no list method find. Sigh. Here's how I'd do it:
> 
> # create a dictionary with each word as key and ordinal as value
> words = dict([(n,m) for m,n in enumerate(("you", "me", "us", "we", 
> "and", "so", "forth"))])
> words["me"] # returns 1 
> 

I assume Bob meant that tuples have no index or find method. His 
suggested procedure will work, but it seems more work than:

 >>> t = ("I'm", "a", "tuple.", "I", "have", "only", "magic", "methods.")
 >>> l = list(t)
 >>> l.index("have")
4
 >>> t[4]
'have'
 >>>

I say more work as the way above builds a list to turn into a 
dictionary. But, since dictionary access is fast, it might be quicker 
for long tuples where the sought item is near then end. If it matters, 
test.

HTH,

Brian vdB