Looping through nested list that contains dictionary

Question

Hi how can I loop through n below, and get the dictionary elements in e if the elements are a match.

e = [(1001, 7005, {'length': 0.35, 'modes': 'cw', 'type': '99', 'lanes': 9}),
     (1002, 8259, {'length': 0.35, 'modes': 'cw', 'type': '99', 'lanes': 9}), (1001, 14007, {'length': 0.35, 'modes': 'cw', 'type': '99', 'lanes': 9})]

n = [[(1001, 7005), (3275, 8925)], [(1598, 6009), (1001, 14007)]]

ie compare n and if n is in e print the dictionary

b = []
for d in n:
    for items in d:
        print b

outcome should be

output = [[{'length': 0.35, 'modes': 'cw', 'type': '99', 'lanes': 9}],[{'length': 0.35, 'modes': 'cw', 'type': '99', 'lanes': 9}]]

score 1 · Answer 1 · answered Mar 31 '14 at 15:23

You can convert the e list to a dictionary, with dictionary comprehension, like this

f = {(v1, v2):v3 for v1, v2, v3 in e}

Then, we can flatten n and check if each of the element is in f or not. If it is there, then we can get the value corresponding to that from f, like this

from itertools import chain
print [f[item] for item in chain.from_iterable(n) if item in f]

Output

[{'lanes': 9, 'length': 0.35, 'modes': 'cw', 'type': '99'},
 {'lanes': 9, 'length': 0.35, 'modes': 'cw', 'type': '99'}]

score 1 · Accepted Answer · edited May 23 '17 at 10:26

You need to create a mapping (dictionary) from the e list and flatten n list of list of tuples into list of tuples:

e = [(1001, 7005, {'length': 0.35, 'modes': 'cw', 'type': '99', 'lanes': 9}),
     (1002, 8259, {'length': 0.35, 'modes': 'cw', 'type': '99', 'lanes': 9}),
     (1001, 14007, {'length': 0.35, 'modes': 'cw', 'type': '99', 'lanes': 9})]

n = [[(1001, 7005),(3275, 8925)], [(1598,6009),(1001,14007)]]

d = {(item[0], item[1]): item[2] for item in e}
n = [item for sublist in n for item in sublist]

print [d[item] for item in n if item in d]

prints:

[{'lanes': 9, 'length': 0.35, 'type': '99', 'modes': 'cw'}, 
 {'lanes': 9, 'length': 0.35, 'type': '99', 'modes': 'cw'}]

Thanks, however the output should be the dictionary alone as @thefourtheye has it — user3481663, Mar 31 '14 at 15:36

venpa · Answer 3 · 2014-03-31T15:44:19.167

0

You can use list comprehension:

[e1[2] for e1 in e for n1 in n for n2 in n1 if (e1[0]==n2[0] and e1[1]==n2[1])]

Output:

[{'lanes': 9, 'length': 0.35, 'type': '99', 'modes': 'cw'}, 
 {'lanes': 9, 'length': 0.35, 'type': '99', 'modes': 'cw'}]

edited Mar 31 '14 at 15:44

answered Mar 31 '14 at 15:29

venpa

4,268
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23

Thanks, however the output should be the dictionary alone as @thefourtheye has it – user3481663 Mar 31 '14 at 15:36
But strangely the output of your code is an empty list on my machine, could it be as a result of different python versions? I use python 2.7 – user3481663 Mar 31 '14 at 16:04

Looping through nested list that contains dictionary

3 Answers3