python - Count unique digits one liner (efficiently)

Question

I'm searching for a way to count unique digits efficiently with a one liner.

For example: given the integer 623562, return value would be 4.

My current way of doing it is, given integer i, im using len(set(str(i))). Creating a set is time consuming. I'm going over alot of numbers so I need an efficient way.

Also, if someone can find a way to go over all the numbers with x digits without using range() (and in a one liner..), I'll be glad. Memory limits me when using range because a list is created (I assume).

Answer 1

sets are optimized for this creation. Unless you want to roll out your own decimal-to-string conversion (and that would take more than one line), it's the way to go.

range only allocates memory in Python 2.x. For small numbers like 623562, the memory shouldn't be a problem. For larger numbers, use xrange in Python 2.x or simply switch to Python 3.x, where range generates the numbers just in time.