Thanks, Steve and Nick. Yes, that's what I need to do. I didn't know it's call "flattening" a list structure but that's precisely what I needed to do.
Steve, I am using 2.3 and so I will go with Nick's version. Thanks to both for helping. "Nick Coghlan" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > It's me wrote: > > Another newbie question. > > > > There must be a cleaner way to do this in Python: > > > > #### section of C looking Python code #### > > a = [[1,5,2], 8, 4] > > a_list = {} > > i = 0 > > for x in a: > > if isinstance(x, (int, long)): > > x = [x,] > > for w in [y for y in x]: > > i = i + 1 > > a_list[w] = i > > print a_list > > ##### > > > > The code prints what I want but it looks so "C-like". How can I make it > > more Python like? > > Firstly, calling your dictionary "a_list" is evil. . . > > Secondly, explaining what you want the code to do in English is handy when > asking for help cleaning up code (since we then know which features are > deliberate, and which are accidental implementation artificacts). > > If I'm reading the code correctly, you want to flatten a data structure which > may contain either substructures or actual elements. > > A custom generator will do nicely: > > Py> def flatten(seq): > ... for x in seq: > ... if hasattr(x, "__iter__"): > ... for y in flatten(x): > ... yield y > ... else: > ... yield x > ... > Py> data = [[1,5,2],8,4] > Py> val_to_pos = {} > Py> for i, x in enumerate(flatten(data)): > ... val_to_pos[x] = i + 1 > ... > Py> print val_to_pos > {8: 4, 1: 1, 2: 3, 4: 5, 5: 2} > > Not any shorter, but this version works correctly for any leaf elements which > don't supply __iter__ (e.g. strings), and internal elements which do (e.g. > tuples) and the depth is limited only by the maximum level of recursion. Don't > try to flatten a circular structure, though :) > > You may not even need to write the generator, since if you have Tkinter, that > already supplies a near-equivalent function: > > Py> from Tkinter import _flatten as flatten > Py> data = [[1,5,2],8,4] > Py> val_to_pos = {} > Py> for i, x in enumerate(flatten(data)): > ... val_to_pos[x] = i + 1 > ... > Py> print val_to_pos > {8: 4, 1: 1, 2: 3, 4: 5, 5: 2} > > It even works with strings as leaf elements: > > Py> data = [["abc","def",2],8,"xyz"] > Py> flatten(data) > ('abc', 'def', 2, 8, 'xyz') > > Cheers, > Nick. > > -- > Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia > --------------------------------------------------------------- > http://boredomandlaziness.skystorm.net -- http://mail.python.org/mailman/listinfo/python-list
