Dictionary with multiple keys in python

Question

12245933,1418,1
12245933,1475,2
134514060,6112,3
134514064,10096,4
12245933,1536,5
...
134514097,16200,38
12245933,1475,39

I want to know for every row[0], the distance of re-occurance of the same value in row[1]

For example:

12245933  has the value 1475 in line 39 and line 2 ..
i want to know all the possible occurrences of 1475 for 12245933 in a file.

Code I tried.

#datafile parser
def parse_data(file):
    pc_elements = defaultdict(list)
    addr_elements = defaultdict(list)
    with open(file, 'rb') as f:
        line_number = 0
        csvin = csv.reader((x.replace('\0','') for x in f), delimiter = ',')
        for row in csvin:
            try:
                pc_elements[int(row[0])].append(line_number)
                addr_elemets[int(row[1])].append(line_number)
                line_number += 1
            except:
                print row
                line_number += 1
                pass

Maybe we can add row[1] as well in pc_elements dict? and get the indexes from that?

is there any other way than using lists? Lists take a long time to process as the size increases. — pistal
– pistal, Commented Feb 28, 2014 at 5:11
I assume first column is kind of id and then you have data for this id. You can create a dict with id's as keys, and value would be a list of tuples representing your data, i.e. {12245933:[(1418,1), (1475,2)]} etc — sashkello
– sashkello, Commented Feb 28, 2014 at 5:15
Hey you can concatenate two keys. i mean number:other and put it in dictionary. — duck
– duck, Commented Feb 28, 2014 at 5:15

zhangxaochen · Accepted Answer · 2014-02-28 05:15:40Z

5

Use tuples as your dictionary keys:

In [63]: d='''
    ...: 12245933,1418,1
    ...: 12245933,1475,2
    ...: 134514060,6112,3
    ...: 134514064,10096,4
    ...: 12245933,1536,5
    ...: 134514097,16200,38
    ...: 12245933,1475,39
    ...: '''

In [64]: from collections import defaultdict
    ...: dic=defaultdict(list)
    ...: for l in d.split():
    ...:     tup=tuple(int(i) for i in l.split(','))
    ...:     dic[tup[:2]].append(tup[2])

In [65]: dic[(12245933, 1475)]
Out[65]: [2, 39]

answered Feb 28, 2014 at 5:15

zhangxaochen

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2 Comments

pistal Over a year ago

this would fail to give the tuples that are existing onlyonce?

zhangxaochen Over a year ago

@pistal what? not sure what do you mean

nappyginger · Accepted Answer · 2014-02-28 05:21:39Z

1

Use nested dictionaries. Map 1224953 to a dictionary which maps 1475 to a list of line numbers where the values occur.

So your final dictionary would look like {1224953 => {1475=>[39, 2]}}

answered Feb 28, 2014 at 5:21

nappyginger

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