How to compare list values with dictionary keys and make a new dictionary of it using python

Question

I have a list like this:

lis = [\'Date\', \'Product\', \'Price\']

I want to compare it with:

dict = {\'Date\' : \'2013-05-0         


        

Answer 1

Treat lis as a set instead, so you can use dictionary views and an intersection:

# python 2.7:
n = {k: d[k] for k in d.viewkeys() & set(lis)}

# python 3:
n = {k: d[k] for k in d.keys() & set(lis)}

Or you could use a simple dict comprehension with a in test against d:

# python 2.6 or older:
n = dict((k, d[k]) for k in lis if k in d)

# python 2.7 and up:
n = {k: d[k] for k in lis if k in d}

This presumes that not all values in lis are going to be in d; the if k in d test can be dropped if they are always going to be present.

For your specific case, the second form is quite a lot faster:

>>> from timeit import timeit
>>> timeit("{k: d[k] for k in d.viewkeys() & s}", 'from __main__ import d, lis; s=set(lis)')
2.156520128250122
>>> timeit("{k: d[k] for k in lis if k in d}", 'from __main__ import d, lis')
0.9401540756225586

Answer 2

filtered_dict = dict((k, original_dict[k]) for k in lis if k in original_dict)

Or if you have 2.7+:

filtered_dict = {k: original_dict[k] for k in lis if k in original_dict}

If you want to use a generator:

item_generator = ((k, original_dict[k]) for k in lis if k in original_dict)

The generator will yield (key, value) pairs.