I also notice that if i do:
def foo():
lookup = collections.defaultdict(list)
x = range(10)
y = range(5, 15)
z = range(8, 22)
sets = {'x': set(x), 'y': set(y), 'z': set(z)}
for key, value in sets.items():
for element in value:
lookup[element].append(key)
for x in lookup:
print x, lookup[x]
print
in oder to print more clearly what I want to see, the sets (as usual
for a mapping type) are not always in order. Note that from 5 to 7 for
example 'y' is listed in front of 'x' and 8 & 9 have 'y', 'x', 'z' and
not 'x', 'y', 'z' ... I am not clear on how to sort that as the
dictionary method lookup.sort() either doesn't work or i have tried
it in all the wrong places.
0 ['x']
1 ['x']
2 ['x']
3 ['x']
4 ['x']
5 ['y', 'x']
6 ['y', 'x']
7 ['y', 'x']
8 ['y', 'x', 'z']
9 ['y', 'x', 'z']
10 ['y', 'z']
11 ['y', 'z']
12 ['y', 'z']
13 ['y', 'z']
14 ['y', 'z']
15 ['z']
16 ['z']
17 ['z']
18 ['z']
19 ['z']
20 ['z']
21 ['z']
On Sep 8, 2009, at 10:52 PM, bob gailer wrote:
kevin parks wrote:
I am looking at this and wondering:
Why does this use collections.defaultdict ?
In fact i guess since collections.defaultdict is new to me i am not
even sure why it exists
and why someone would use this as opposed to using Python's built-
in dictionary? and why was it
used in this instance?
It simplifies coding, as it takes care of initializing each new
entry to a list.
On Sep 6, 2009, at 3:06 AM, bob gailer wrote:
I want to be able to look at a number/item and see which lists it
is in so that i could maybe have a master list of all the data, a
superset, and then an indication of which lists that data was in,
as some items will only be in one list, some will appear in two
lists (x & y, or x & z or y & z) and a small handful will be in
all three lists.
I think you mean "set" rather than "list"
To enable processing of an arbitrary number of sets, put them in a
collection (list or dictionary). Use a list if it is sufficient to
identify sets by number, else use a dictionary.
Use a dictionary to relate items to their set(s).
import collections
lookup = collections.defaultdict(list)
sets = {'x': set((1,2,3)), 'y': set((2,3))}
for key, value in sets.items():
for element in value:
lookup[element].append(key)
print lookup
--
Bob Gailer
Chapel Hill NC
919-636-4239
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