This function solve the issue of random.shuffle that is based only on randomized shuffling (that's not a real shuffling, because many times items returned aren't shuffled enough).
This function make a randomized shuffle and after this loops long the list resorting to avoid two items with a same value in a given attribute.
When shuffling is over and there are duplicates, they are leftover to the end (and you can remove them if you set 'remove_duplicates' to True)
Run it in a separated file to see it in action.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 | import random
try:
set
except:
from sets import Set as set
def _get_value(obj, attr):
if not attr:
return obj
elif isinstance(obj, dict):
return obj[attr]
else:
return getattr(obj, attr)
def all_are_duplicates(items, attr=None):
"""Returns True if all given items has the same value for a given attribute"""
return len(set([_get_value(item, attr) for item in items])) == 1
def real_shuffle(l, attr=None, remove_duplicates=False):
"""This function make a 'real' shuffle of a list, without only depend on a
randomized shuffling but looping along the list to make sure they aren't
repeating a given attribute."""
# Make a copy of the list
ret = list(l)
# Just returns it if has 1 or less items
if len(ret) <= 1:
return ret
# Randomic shuffling
random.shuffle(ret)
# Loop along the list to make 'real' shuffle
new_list = []
while not all_are_duplicates(ret, attr):
for cur_index in range(len(ret)):
if not new_list or _get_value(ret[cur_index], attr) != _get_value(new_list[-1], attr):
new_list.append(ret.pop(cur_index))
break
new_list += ret
# Remove the duplicates
if remove_duplicates:
while len(new_list) > 1 and _get_value(new_list[-1], attr) == _get_value(new_list[-2], attr):
new_list.pop(-1)
return new_list
if __name__ == '__main__':
class Animal(object):
name = str()
kind = str()
def __init__(self, name, kind):
self.name, self.kind = name, kind
def __str__(self):
return '%s/%s'%(self.name, self.kind)
animals = [
Animal('a1', 'lion'),
Animal('b1', 'tiger'),
Animal('a2', 'lion'),
Animal('a3', 'lion'),
Animal('a5', 'lion'),
Animal('c1', 'lion'),
Animal('a4', 'lion'),
Animal('b2', 'tiger'),
Animal('b3', 'tiger'),
Animal('a6', 'lion'),
Animal('c2', 'cat'),
Animal('b4', 'tiger'),
]
print all_are_duplicates(animals, 'kind'), all_are_duplicates(animals[2:5], 'kind')
print '\n\nOriginal:'
print ' ', ', '.join(map(str, animals))
print '\n\nShuffled by Python'
animals2 = list(animals)
random.shuffle(animals2)
print ' ', ', '.join(map(str, animals2))
print '\n\nShuffled by me'
animals3 = real_shuffle(animals, 'kind')
print ' ', ', '.join(map(str, animals3))
print '\n\nShuffled by me - removing duplicates'
animals3 = real_shuffle(animals, 'kind', True)
print ' ', ', '.join(map(str, animals3))
print '\n\n'
|
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