[madsbjoern]

Hi

I've noticed a strange behavior in the dictionary objects - when I add three different keys, let's just say:

q={}
q[u'Image1']=u'path1'
q[u'XMLfile1']=u'path2'
q[u'Image2']=u'path3'

and print the keys:

q.keys()

it outputs the keys in alphabeticel order and not the order it was added:

[u'Image2', u'Image1', u'XMLfile1']

Does anyone know whether it possible to get the keys in the order it was added?

[jethro.fn]

Originally Posted by madsbjoern

q.keys()

it outputs the keys in alphabeticel order and not the order it was added:

[u'Image2', u'Image1', u'XMLfile1']

Does anyone know whether it possible to get the keys in the order it was added?

This is documented behaviour of the dictionary object, i.e. it will not preserve any order, alphabetical or otherwise. It was just a coincidence that you got your keys in alphabetical order.

From http://www.python.org/doc/2.2.2/lib/typesmapping.html:

(3)

Keys and values are listed in random order. If items(), keys(), values(), iteritems(), iterkeys(), and itervalues() are called with no intervening modifications to the dictionary, the lists will directly correspond. This allows the creation of (value, key) pairs using zip(): "pairs = zip(a.values(), a.keys())". The same relationship holds for the iterkeys() and itervalues() methods: "pairs = zip(a.itervalues(), a.iterkeys())" provides the same value for pairs. Another way to create the same list is "pairs = [(v, k) for (k, v) in a.iteritems()]".

To preserve insertion order, insert the keys in an auxiliary list. You can even create your own type that does it automatically, by wrapping the built-in dictionary.

[cyke64]

Originally Posted by madsbjoern

Hi

I've noticed a strange behavior in the dictionary objects - when I add three different keys, let's just say:

q={}
q[u'Image1']=u'path1'
q[u'XMLfile1']=u'path2'
q[u'Image2']=u'path3'

and print the keys:

q.keys()

it outputs the keys in alphabeticel order and not the order it was added:

[u'Image2', u'Image1', u'XMLfile1']

Does anyone know whether it possible to get the keys in the order it was added?

As jethro said to you it's the usual behavior of dictionnary in Python
But it exists implementation of ordered dictionary
I already put one link on it in the wiki
Look at odict !

Cyke64

[madsbjoern]

Originally Posted by jethro.fn

To preserve insertion order, insert the keys in an auxiliary list. You can even create your own type that does it automatically, by wrapping the built-in dictionary.

Thanks - that's what I expected. Good idea with an auxiliary list, i'll solve it that way.

/Mads

[madsbjoern]

Originally Posted by cyke64

As jethro said to you it's the usual behavior of dictionnary in Python
But it exists implementation of ordered dictionary
I already put one link on it in the wiki
Look at odict !

Cyke64

All right, i'll have a look

[Skarabeus]

>>>q={}
>>>q[u'Image1']=u'path1'
>>>q[u'XMLfile1']=u'path2'
>>>q[u'Image2']=u'path3'
>>>l=q.keys()
>>>l.sort()
>>>l
[u'Image1', u'Image2', u'XMLfile1']

Bye.