creating nested dictionary with multiple values from a mysql row fetchall using python

Question

consider i'm getting out from a row where row[0],row[1],row[2] consists of below output and it comes in same order as below:

'Testcase2', 37L, 'hydra.c
'Testcase2', 100L,'vendor.c
'Testcase7', 34L, 'template.c
'Testcase3', 88L, 'hydra.c
'Testcase3', 80L, 'vendor.c
'Testcase6', 81L, 'template.c
'Testcase1', 1L, 'hydra.c
'Testcase4', 89L, 'vendor.c
'Testcase8', 41L, 'template.c
'Testcase5', 83L, 'vendor.c
'Testcase4', 98L, 'template.c

i need a unique test case names to be printed along with maximum row[1] value so i thought of creating dictionary with multiple values.

{'Testcase1': {'hydra.c': 1},
 'Testcase2':{'hydra.c':37,'vendor.c':100 },
 'Testcase3':{'hydra.c':1,'vendor.c':80}
 'Testcase4':{'vendor.c':89,'template.c':98},
 'Testcase5':{'vendor.c':83}
 'Testcase6':{'template.c':34}....}

for creating dictionary with multiple values as above please do help me so that later i will do sorting of nested dict so that later i ll print testcase name with highest row[1] value:

from pprint import pprint as pp
d={}
for x,y,z in row:
    d.setdefault(x,{z:[]})
    d[x][z].append(y)

pp(d)

i tried above code but its updating only with new file name its not appending as above requirement.

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Jack Ryan
– Jack Ryan

2017-11-21 04:43:43 +00:00
Commented Nov 21, 2017 at 4:43 — Jack Ryan
– Jack Ryan, Commented Nov 21, 2017 at 4:43
And what have you tried in order to achieve this?

roganjosh
– roganjosh

2017-11-21 05:01:47 +00:00
Commented Nov 21, 2017 at 5:01 — roganjosh
– roganjosh, Commented Nov 21, 2017 at 5:01
i have added my code

vinay
– vinay

2017-11-21 05:08:26 +00:00
Commented Nov 21, 2017 at 5:08 — vinay
– vinay, Commented Nov 21, 2017 at 5:08

J_H · Accepted Answer · 2017-11-21 05:59:28Z

1

Append is a list operation. Based on your example data, it appears you anticipate distinct z's for a given x:

    for x, y, z in row:
        if x not in d:
            d[x] = {}
        d[x][z] = y

But that if is a common pattern addressed in collections:

from collections import defaultdict

    d = defaultdict(dict)
    for x, y, z in row:
        d[x][z] = y

answered Nov 21, 2017 at 5:59

J_H

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3 Comments

vinay Over a year ago

how to sort 'd' based on value 'y'

J_H Over a year ago

A dict makes no promises about being sorted. You'll want some sortable data structure, such as a list. Initialize with lst = [], and after assigning d[x][z] = y, also do lst.append((y, x, z)) (or the tuple y, z, x if that is what your question was asking). Then sorted(lst) gives the desired result. To make it look nice, use pprint.pprint(sorted(lst)).

dozyaustin Over a year ago

A revision to this if x not in d: d[x] = {} d[x][z] = y is needlessly slow this is faster: going with try/except KeyError catch is way faster.

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