# Learning Pyhton - Functional Programming - How intersect/difference two dict with dict/values? fast!

macm moura.mario at gmail.com
Wed Nov 10 21:42:53 CET 2010

```... and this works!

>>> def intersect(s1, s2):
...     d = {}
...     e = {}
...     r1 = filter(s1.has_key, s2.keys())
...     for x in r1:
...         d[x]= filter(lambda z:z in s1[x][0],s2[x][0])
...         if len(d[x]) > 0:
...             e[x] = d[x]
...     return e
...
>>> intersect(dict1,dict2)
{'ac': [1, 3, '79b'], 'ab': [2]}
>>>

but how I pass d[x] and make the filter?

>>> result = [filter(lambda z:z in dict1[x][0],dict2[x][0]) for x in filter(dict1.has_key, dict2.keys())]
>>> result
[[], [1, 3, '79b'], [2]]
>>>

but should be {'ac': [1, 3, '79b'], 'ab': [2]}

Best Regards

Mario

On 10 nov, 18:14, macm <moura.ma... at gmail.com> wrote:
> Hi Folks
>
> I am studing yet (with fever, grasp and headache).
>
> I know I can do better, but first I should learn more about
> "dictionary comprehension syntax" in python 2.65
>
> >>> dict1 = {'ab':[[1,2,3,'d3','d4',5],12],'ac':[[1,3,'78a','79b'],54],'ad': [[56,57,58,59],34], 'ax': [[56,57,58,59],34]}
> >>> dict2 = {'ab':[[22,2,'a0','42s','c4','d3'],12],'ab':[[2,4,50,42,'c4'],12],'ac':[[1,3,'79b',45,65,'er4'],54],'ae': [[56,57,58,59],34],'ax':[[9],34]}
>
> >>> # Arnaud Delobelle
>
> ... def intersectList(iterables):
> ...     nexts = [iter(iterable).next for iterable in iterables]
> ...     v = [next() for next in nexts]
> ...     while True:
> ...         for i in xrange(1, len(v)):
> ...             while v[0] > v[i]:
> ...                 v[i] = nexts[i]()
> ...             if v[0] < v[i]: break
> ...         else:
> ...             yield v[0]
> ...         v[0] = nexts[0]()
> ...>>> defintersect(s1, s2):
>
> ...     d = {}
> ...     e = {}
> ...     r1 = filter(s1.has_key, s2.keys())
> ...     for x in r1:
> ...         d[x] = list(intersectList([s1[x][0],s2[x][0]]))
> ...         if len(d[x]) > 0:
> ...             e[x] = d[x]
> ...     return e
> ...>>>intersect(dict1,dict2)
>
> {'ac': [1, 3, '79b'], 'ab': [2]}
>
>
>
> Best Regards
>
> Mario
>
> On 10 nov, 07:51, Paul Rudin <paul.nos... at rudin.co.uk> wrote:
>
> > Lawrence D'Oliveiro <l... at geek-central.gen.new_zealand> writes:
> > > In message <mailman.787.1289336127.2218.python-l... at python.org>, Terry Reedy
> > > wrote:
>
> > >> To echo John Nagle's point, if you want non-masochist volunteers to read
> > >> your code, write something readable like:
>
> > >> dict1 = {'ab': [[1,2,3,'d3','d4',5], 12],
> > >>           'ac': [[1,3,'78a','79b'], 54],
> > >>           'ad': [[56,57,58,59], 34],
> > >>           'ax': [[56,57,58,59], 34]}
>
> > > How come Python itself doesn’t display things that way?
>
> > try: pprint.pprint(dict1)
>
>

```