Python set difference not working
<p>In the following code;</p>

<pre><code>all_digits = set(range(10))
print all_digits
for i in range(102,167):
    digits = set(k for k in (str(i)))
    if len(digits) != 3:
        continue
    print "digits:", digits
    remaining_digits = all_digits - digits
    print "remaining:", remaining_digits
</code></pre>

<p>The digits set contains 3 elements. I want a set difference of them, however, <code>remaining_digits</code> always have all digits. What am I doing wrong here?
Here is a sample from output I am getting;</p>

<pre><code>set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
digits: set(['1', '0', '2'])
remaining: set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
digits: set(['1', '0', '3'])
remaining: set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
digits: set(['1', '0', '4'])
remaining: set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
digits: set(['1', '0', '5'])
remaining: set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
digits: set(['1', '0', '6'])
remaining: set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
digits: set(['1', '0', '7'])
remaining: set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
digits: set(['1', '0', '8'])
remaining: set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
</code></pre>
