CODEWITHSUNDEEP
pythondictionary
siva
siva

Reputation: 2145

Python: Adding dictionary values to form new tuple-keyed dictionary

If I have a dictionary as follows (with some lists):

units = ['a','b']
nums = ['1','2']
ratios = ['alpha', 'beta']

d = {'a_1_alpha':4, 'a_1_beta' :1, 'a_2_alpha' :2, 'a_2_beta': 3, 'b_1_alpha':2}

How do i from a new dictionary which:

i.e.

new_d = { ('1','alpha'): 6, ('1','beta'): 1, ('2','alpha'): 2, ('2','beta'): 3}

I have the following code, but doesn't seem right.

new_d = {}
for num in nums:
    for ratio in ratios:
        for k,v in d.items():
            if ratio in k:
                try:
                    oldval = dict[num,ratio]
                except:
                    oldval = 0
                new_d[(num,ratio)] = oldval + v

for p,q in new_d.items():
    print p,q

Please help to comment/advice. Thanks :).

Upvotes: 0

Views: 1160

Answers (3)

Artsiom Rudzenka
Artsiom Rudzenka

Reputation: 29093

OR using collections module:

d = {'a_1_alpha':4, 'a_1_beta' :1, 'a_2_alpha' :2, 'a_2_beta': 3, 'b_1_alpha':2}

from collections import defaultdict

new_d = defaultdict(int)

for k,v in ((tuple(k.split('_')[1:]),v) for k,v in d.iteritems()):
    new_d[k] += v

Upvotes: 2

Bolo
Bolo

Reputation: 11690

The two outer loops are redundant, simply iterate over the key-value pairs of d. You can easily extract the three components of a key using split(). Here's the code:

new_d = {}
for k, v in d.items():
   u, n, r = k.split('_')
   new_d[(n, r)] = v + new_d.get((n, r), 0)

Upvotes: 6

Morten Kristensen
Morten Kristensen

Reputation: 7613

This should solve your problem:

new_d = {}
for n in nums:
    for r in ratios:
        for k, v in d.items():
            if r in k and n in k:
                try:
                    old = new_d[(n, r)]
                except:
                    old = 0
                new_d[(n, r)] = v + old

for p, q in new_d.items():
    print (p, q)

Btw. you also forgot to check that n in k when determining whether the key is viable.

Upvotes: 2

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