using iterator on a dictionary

Dev Shed Forums Sponsor:

November 21st, 2003, 12:47 PM

sad.machine

I hate nerds

Join Date: Jul 2003

Posts: 540

Time spent in forums: 21 h 28 m 44 sec
Reputation Power: 0

using iterator on a dictionary

how do you iteratre through a dictionaries keys? i see that a dictionary has iterkeys() that returns an iterator over the ekys, but i have no idea how to use the iterator object and documentation on the web stinks

November 21st, 2003, 03:48 PM

netytan

Hello World :)

Join Date: Mar 2003

Location: Hull, UK

Posts: 2,537

Time spent in forums: 1 Week 2 Days 18 h 17 m 47 sec
Reputation Power: 68

There are actually a few ways you can iterate over a dictionary, so you dont have to use an iterator anyway.. but heres a few working examples anyway!

Code:

dictionary = {'1': 'one', '2': 'two', '3': 'there'}

for key in dictionary.iterkeys():
    print key, dictionary[key]

Code:

dictionary = {'1': 'one', '2': 'two', '3': 'there'}

for key in dictionary.keys():
    print key, dictionary[key]

Code:

dictionary = {'1': 'one', '2': 'two', '3': 'there'}

for key, value in dictionary.items():
    print key, value

Mark.

__________________
programming language development: www.netytan.com – Hula

November 21st, 2003, 04:17 PM

Grim Archon

Mini me.

Join Date: Nov 2003

Location: Cambridge, UK

Posts: 783

Folding Points: 1488 Folding Title: Novice Folder

Time spent in forums: 3 Days 2 h 15 m 57 sec
Reputation Power: 12

Here's another...

In python 2.2,2.3 you can iterate directly over dictionaries because they contain an iterator object. The dictionary iterator will return the next key in the un-ordered list of keys. So you can do this

Code:

a = {"tom":2.3,"****":21.1,"harry":1.1}
for key in a:
    print key, a[key]

where in calls the next method of the iterator.

I just noticed you can't use *Richard* in an example!

November 21st, 2003, 04:23 PM

percivall

Contributing User

Join Date: Jul 2003

Posts: 133

Time spent in forums: < 1 sec
Reputation Power: 10

There's also the dict.items(), which returns a tuple containing the key and the value.

Code:

>>> for (key, item) in {1:2,2:3,3:4}.items():
...   print key, item
... 
1 2
2 3
3 4
>>>

I know you asked for the keys, but it's useful sometimes to get the item straight-away.

November 21st, 2003, 04:34 PM

netytan

Hello World :)

Join Date: Mar 2003

Location: Hull, UK

Posts: 2,537

Time spent in forums: 1 Week 2 Days 18 h 17 m 47 sec
Reputation Power: 68

i kinda already gave an example of this one Perc

November 24th, 2003, 08:16 AM

percivall

Contributing User

Join Date: Jul 2003

Posts: 133

Time spent in forums: < 1 sec
Reputation Power: 10

Hmm. Didn't see that example earlier. You sure you didn't add it after?

November 24th, 2003, 09:13 AM

netytan

Hello World :)

Join Date: Mar 2003

Location: Hull, UK

Posts: 2,537

Time spent in forums: 1 Week 2 Days 18 h 17 m 47 sec
Reputation Power: 68

The advantages of being mod boy

.. Naw, to my regret i cant get around that anoying last edited line

Mark.

using iterator on a dictionary

Developer Shed Advertisers and Affiliates