How to filter a dictionary according to an arbitrary condition function

Question

I have a dictionary of points  say    gt  gt  gt  points   a   3 4    b   1 2    c   5 5    d   3 3     I want to create a new dictionary with all the points whose x and y value is smaller than 5  i e  points  a    b  and  d    According to the the book  each dictionary has the items   function  which returns a list of  key  pair   tuple    gt  gt  gt  points items      a    3  4      c    5  5      b    1  2      d    3  3      So I have written this    gt  gt  gt  for item in  i for i in points items   if i 1  0  lt 5 and i 1  1  lt 5           points small item 0   item 1       gt  gt  gt  points small   a    3  4    b    1  2    d    3  3     Is there a more elegant way  I was expecting Python to have some super-awesome dictionary filter f  function

User · Answer

dict  k  v  for k  v in points items   if all x  lt  5 for x in v     You could choose to call  iteritems   instead of  items   if you re in Python 2 and points may have a lot of entries   all x  lt  5 for x in v  may be overkill if you know for sure each point will always be 2D only  in that case you might express the same constraint with an and  but it will work fine -

User · Answer

Nowadays  in Python 2 7 and up  you can use a dict comprehension    k  v for k  v in points iteritems   if v 0   lt  5 and v 1   lt  5    And in Python 3    k  v for k  v in points items   if v 0   lt  5 and v 1   lt  5

User · Answer

gt  gt  gt  points     a    3  4    c    5  5    b    1  2    d    3  3    gt  gt  gt  dict filter lambda x   x 1  0   x 1  1    lt   5  5   points items        a    3  4    b    1  2    d    3  3

User · Answer

dict  k  v  for  k  v  in points iteritems   if v 0   lt  5 and v 1   lt  5

User · Answer

dict  k  v  for  k  v  in points iteritems   if v 0   lt  5 and v 1   lt  5

User · Answer

I think that Alex Martelli s answer is definitely the most elegant way to do this  but just wanted to add a way to satisfy your want for a super awesome dictionary filter f  method in a Pythonic sort of way   class FilterDict dict       def   init   self  input dict           for key  value in input dict iteritems                self key    value     def filter self  criteria           for key  value in self items                if  criteria value                    self pop key   my dict   FilterDict    a   3 4    b   1 2    c   5 5    d   3 3     my dict filter lambda x  x 0   lt  5 and x 1   lt  5    Basically we create a class that inherits from dict  but adds the filter method  We do need to use  items   for the the filtering  since using  iteritems   while destructively iterating will raise exception

User · Answer

points small   dict filter lambda  a  b c    b lt 5 and c  lt  5  points items

[python] How to filter a dictionary according to an arbitrary condition function?

Examples related to python

Examples related to dictionary

Examples related to filter