Python code that will find words made out of specific letters. Any subset of the letters could be used

Question

If I have a list of words in the variable words and a list of letters in the variable letters, how can I find all the words that can be made up out of the letters in letters

Answer 1

you can use all() along with sets, because they allow O(1) membership checkup:

In [9]: words = ['dummy', 'australia']

In [10]: letters = ['a', 'b', 'i', 'l', 'r', 's', 't', 'u']

In [11]: let_set=set(letters)

In [12]: for word in words:
    if all(x in let_set for x in set(word)):
        print word
   ....:         
australia

Answer 2

This employs set intersection, which might be faster. On the other hand, it requires additional memory.

letters = ['a', 'b', 'i', 'l', 'r', 's', 't', 'u']
words = ['dummy', 'australia', 'australians' ]

f = set(letters)
c = [ (word, set(word)) for word in words ]
# changing to s & f == f makes condition "must use ALL letters"
s = [ w for (w, s) in c if s & f == s ]

s is now ['australia']

(But I'm curious about the use of such a solution. A Scrabble robot? A dusty-keyboard attack on dictionary passwords? )

Answer 3

Use regular expressions:

>>> import re
>>> m = re.compile('^[abilrstu]+$')
>>> m.match('australia') is not None
True
>>> m.match('dummy') is not None
False
>>> m.match('australian') is not None
False

Answer 4

This is probably the easiest way:

result = [w for w in words if all(i in letters for i in w)]

This returns ['australia']