[ python-Feature Requests-1548178 ] Add 'find' method to sequence types

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Feature Requests item #1548178, was opened at 2006-08-28 13:47
Message generated for change (Comment added) made by josiahcarlson
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Category: Python Interpreter Core
Group: None
Status: Open
Resolution: None
Priority: 4
Submitted By: kovan (kovan)
Assigned to: Nobody/Anonymous (nobody)
Summary: Add 'find' method to sequence types

Initial Comment:
In the benefit of Python's readability and simplicity,
a 'find' method could be added to sequence types, that
would return the first item in the list that matches
some criteria.
For example, it's a common practice to use lists of
(key,value) pairs instead of dictionaries when the
sequence must be ordered.
To find an element maching a key in such cases, I
frequently find myself writing (IMHO) too much code for
such a straightforward operation. AFAIK currently there
are two easy ways to do this (shouln't be one, and only
one?):

for item in items:
  if item.attribute == key:
    foundItem = item
    break
else: foundItem = None

OR

foundItems = [item for item in items if item.key ==  value]
if foundItems:
  foundItem = foundItem[0]

IMO, in none of the cases the code is as clear and,
specially, as short, as it should be.

With the find method, the same code would be:

item = items.find(lambda x: x.key == value)

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Comment By: Josiah Carlson (josiahcarlson)
Date: 2006-09-03 12:07

Message:
Logged In: YES 
user_id=341410

Lists have an .index(obj[, start[, stop]]) method that tells
you the index of the first object that matches obj, raising
an exception otherwise.

Generally speaking, you can get better performance for
repeated searches by...

dct = {}
for i,(k,v) in enumerate(lst):
    dct.setdefault(k, []).append(i)

Then to find the first index...

dct.get(k, [None])[0]

Suggested close.

----------------------------------------------------------------------

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