[Tutor] Question about sorting a list within a dictionary within a list

[ian douglas]

I'm using the Bono library for talking to EC2, and I'm getting a list of 
EC2 instances back in a list called "reservations". Each element in the 
list is a dictionary of information. One of those dictionary elements is 
a list called 'instances', and I only ever care about the first entry. 
That instances[0] value is a dictionary, which holds a key I want to use 
to sort the base "reservations" list.

I found this helpful bit for sorting a list of dictionaries by a key 
within the dictionaries:
http://stackoverflow.com/questions/72899/in-python-how-do-i-sort-a-list-of-dictionaries-by-values-of-the-dictionary

... this works great if you just have a list of dictionaries. I'm not 
sure how to go deeper within that to sort my data without iterating 
through the entire 'reservations' list and building an entirely new 
list. Maybe it would be easier, but I'm just curious if it's possible 
without messing with my main 'reservations' list.


My current code looks like this: (it's a views.py file)

from django.http import HttpResponse
import boto.ec2
from operator import itemgetter

def index(request):
     conn = boto.connect_ec2()
     reservations = conn.get_all_instances()

     # this is where I'm trying to sort everything
     res_sorted = sorted(reservations, key=itemgetter('launch_time'))

     output = '<table>'
     output += '<tr>'
     output += '<th>State</th>'
     output += '<th>Launched</th>'
     output += '<th>Public Hostname</th>'
     output += '<th>Public IP</th>'
     output += '<th>Private Hostname</th>'
     output += '<th>Private IP</th>'
     output += '</tr>'
     for reservation in res_sorted:
         instance = reservation.instances[0]
         output += '<tr>'
         output += '<td>' + instance.state + '</td>'
         output += '<td>' + instance.launch_time + '</td>'
         output += '<td>' + instance.public_dns_name + '</td>'
         output += '<td>' + instance.ip_address + '</td>'
         output += '<td>' + instance.private_dns_name + '</td>'
         output += '<td>' + instance.private_ip_address + '</td>'


Ideally, I'd like to make each table column 'sortable' so the user can 
click on state/launched/etc (I may add more columns in the future), but 
I'm not sure how to search deeper within the 'reservations' list for the 
sorted() call to get at the 'launch_time' element within the instaces[0] 
dictionary.

Also, I'm sure there are much better ways to do the display logic, but 
I'll tackle that another time.

Thanks for any pointers,
Ian

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