itertools.product
accepts a repeat
keyword that you can use:
In [92]: from itertools import product
In [93]: word = "L0B7B0B5"
In [94]: subs = product("68", repeat=word.count("B"))
In [95]: list(subs)
Out[95]:
[('6', '6', '6'),
('6', '6', '8'),
('6', '8', '6'),
('6', '8', '8'),
('8', '6', '6'),
('8', '6', '8'),
('8', '8', '6'),
('8', '8', '8')]
Then one fairly concise method to make the substitutions is to do a reduction operation with the string replace
method:
In [97]: subs = product("68", repeat=word.count("B"))
In [98]: [reduce(lambda s, c: s.replace('B', c, 1), sub, word) for sub in subs]
Out[98]:
['L0676065',
'L0676085',
'L0678065',
'L0678085',
'L0876065',
'L0876085',
'L0878065',
'L0878085']
Another method, using a couple more functions from itertools
:
In [90]: from itertools import chain, izip_longest
In [91]: subs = product("68", repeat=word.count("B"))
In [92]: [''.join(chain(*izip_longest(word.split('B'), sub, fillvalue=''))) for sub in subs]
Out[92]:
['L0676065',
'L0676085',
'L0678065',
'L0678085',
'L0876065',
'L0876085',
'L0878065',
'L0878085']