erikrose/more-itertools — pull request #44 by bbayles (2014-07-31 03:47:55+00:00)
Title: Add unique_from_each() function

Some months after answering [this](http://stackoverflow.com/questions/17035577/unique-features-between-multiple-lists/17035741#17035741) question at StackOverflow, I had a need for a function that would give me the unique items from a list of lists.

Here are some examples:

````python
>>> unique_from_each("mississippi", "missouri")
[['p', 'p'], ['o', 'u', 'r']]
>>> unique_from_each("mississippi", "missouri", "russian")
[['p', 'p'], ['o'], ['a', 'n']]
````
`mississippi` and `missouri` both have an `m`, some instances of `i`, and some instances of `s`. The former doesn't have an `o`, a `u`, or an `r`, though. And the latter doesn't have a `p`, let alone two.

If we add `russian` to the mix, there's no additional overlap with `mississippi`, but it shares `r` and `u` with `missouri`. It's the only one with an `n`.

For my application I needed order and duplicates to be preserved, so as-written this doesn't do anything with sets.

It seems itertools-y, so I'd like to submit it to be considered for more-itertools.