Rebuild list of objects with redundancies on objects' attribute

[Nico Grubert]

Hi there

I have a list of dummy objects which have the attributes 'location',
'name', 'gender'.
Now I want to rebuild this list in order to avoid redundancies on
objects with the same 'location'.

Example:

#------------------------------------------------------------------
class Dummy:
pass

a = Dummy()
a.location = 'tokio'
a.name = 'john'
a.gender = 'm'

b = Dummy()
b.location = 'tokio'
b.name = 'peter'
b.gender = 'm'

c = Dummy()
c.location = 'madrid'
c.name = 'susan'
c.gender = 'f'

d = Dummy()
d.location = 'london'
d.name = 'alex'
d.gender = 'm'

persons = [a, b, c, d]

print "loc name gender"
print "---------------------"
for obj in persons:
print "%s - %s - %s" % (obj.location, obj.name, obj.gender)

#------------------------------------------------------------------

The output reads like this:

loc name gender
---------------------
tokio john m
tokio peter m
madrid susan f
london alex m

I want to create this list (where name and gender are lists):
loc name gender
-----------------------------
tokio [john, peter] [m]
madrid [susan] [f]
london [alex] [m]

How can I do this?


Thanks in advance.
Nico

 

[Peter Otten]

Hi there

I have a list of dummy objects which have the attributes 'location',
'name', 'gender'.
Now I want to rebuild this list in order to avoid redundancies on
objects with the same 'location'.

Example:

#------------------------------------------------------------------
class Dummy:
pass

a = Dummy()
a.location = 'tokio'
a.name = 'john'
a.gender = 'm'

b = Dummy()
b.location = 'tokio'
b.name = 'peter'
b.gender = 'm'

c = Dummy()
c.location = 'madrid'
c.name = 'susan'
c.gender = 'f'

d = Dummy()
d.location = 'london'
d.name = 'alex'
d.gender = 'm'

persons = [a, b, c, d]

print "loc name gender"
print "---------------------"
for obj in persons:
print "%s - %s - %s" % (obj.location, obj.name, obj.gender)

#------------------------------------------------------------------

The output reads like this:

loc name gender
---------------------
tokio john m
tokio peter m
madrid susan f
london alex m

I want to create this list (where name and gender are lists):
loc name gender
-----------------------------
tokio [john, peter] [m]
madrid [susan] [f]
london [alex] [m]

How can I do this?

Put the persons into a dictionary using the location as key

from collections import defaultdict
groups = defaultdict(list)
for p in persons:
groups[p.location].append(p)

Below is a spoiler that uses itertools.groupby(), but you learn more if you
try to work it out yourself



from itertools import groupby

def location(p):
return p.location

persons.sort(key=location)
print "loc name gender"
print "---------------------"
for loc, group in groupby(persons, key=location):
group = list(group)
genders = sorted(set(p.gender for p in group))
names = sorted(p.name for p in group)
print "%s - %s - %s" % (loc, names, genders)

Peter