Ordered dictionary?

[Leif K-Brooks]

I need to associate a string (key) with an integer (value). A dictionary
would do the job, except for the fact that it must be ordered. I also
need to look up the value for a specific key easily, so a list of tuples
wouldn't work.

[Carmine Moleti]

Hi Dragos,

def filterList(p_li st, p_value):
l_len = len(p_list)
l_temp = map(None, (p_value,)*l_le n, p_list)
l_temp = filter(lambda x: x[1].find(x[0])==0, l_temp)
return map(operator.ge titem, l_temp, (-1,)*len(l_temp) ) phones_dict = {'jansen' : '0000', 'xxx' : '1111', 'jan2' : '2222'}
names_list = filterList(phon es_dict.keys(), 'jan')
phones_list = map(phones_dict .get, names_list) This extracts from the dictionary the telephone(value s) numbers for
names(keys) starting with 'jan'...

Why you didn't used the string.startswi th(...) method?

I wrote this:

d={'carmine':'1 23456','carmela ':'4948399','pi ppo':'39938303' }
for name,number in d.items():
if name.startswith ('car'):
print name,number

This also extract from the dictionay all the (name,number) pairs whose
name starts with a given substring ('car' in the example).

Thanks for your answer

[Josiah Carlson]

Carmine Moleti wrote:

Hi Dragos,

def filterList(p_li st, p_value):
l_len = len(p_list)
l_temp = map(None, (p_value,)*l_le n, p_list)
l_temp = filter(lambda x: x[1].find(x[0])==0, l_temp)
return map(operator.ge titem, l_temp, (-1,)*len(l_temp) )

phones_dict = {'jansen' : '0000', 'xxx' : '1111', 'jan2' : '2222'}
names_list = filterList(phon es_dict.keys(), 'jan')
phones_list = map(phones_dict .get, names_list)

This extracts from the dictionary the telephone(value s) numbers for
names(keys) starting with 'jan'...

Why you didn't used the string.startswi th(...) method?

I wrote this:

d={'carmine':'1 23456','carmela ':'4948399','pi ppo':'39938303' }
for name,number in d.items():
if name.startswith ('car'):
print name,number

This also extract from the dictionay all the (name,number) pairs whose
name starts with a given substring ('car' in the example).

Thanks for your answer

Something strange is that for short 'other' strings
string[:len(other)] == other
#is faster than
string.startswi th(other)

Maybe find is faster than startswith.

- Josiah

[David M. Wilson]

"Paul McGuire" <pt***@users.so urceforge.net> wrote...

If you really need to access the dictionary in sorted key order, is this so
difficult?

That was not the original poster's question. Order is semantic
information which a dictionary does not record or represent in any
way.
David.

[Terry Reedy]

> Well I too sometimes need the keys in a dictionary to be sorted and your

solutions wouldn't help. The problem is the following.

I have a number of key value pairs, like names and telephone numbers.
Just more subject to change. Now I want the telephone numbers of everyone whose name starts with "jan".

Or I just inserted a name and want to know who is alphabetically next.
Or I want to know who is first or last.

A python dict is not very well suited to this, especially for large numbers
of key,value pairs. However, if you do pull out sorted lists of keys, use
the bisect module to find specific keys. log(n) behavior is fine.

A table with a btree index is designed for the things your want to do.
There is a btree,py in zope (by Tim Peters, I believe), but I do not know
how 'extractable' it is. You could search the archives.

Terry J. Reedy

[Mel Wilson]

In article <99************ **************@ posting.google. com>,
dw***********@b otanicus.net (David M. Wilson) wrote:

"Paul McGuire" <pt***@users.so urceforge.net> wrote...

If you really need to access the dictionary in sorted key order, is this so
difficult?

That was not the original poster's question. Order is semantic
information which a dictionary does not record or represent in any
way.

Wants order of insertion. Best I can think of is

class OrderedDict (dict):
"Retains order-of-insertion in the dictionary"
def __setitem__ (self, key, value):
dict.__setitem_ _ (self, key, (len (self), value,) )

def __getitem__ (self, key):
return dict.__getitem_ _ (self, key)[1]

def ordered_items (self):
i = [(v, k) for (k, v) in self.items()]
i.sort()
return [(k, v[1]) for (v, k) in i]

# end class OrderedDict

if __name__ == '__main__':
D = OrderedDict()
D['oranges'] = 41
D['lemons'] = 22
D['limes'] = 63

print D
print D.ordered_items ()

Possibly other refinenemts: __init__ that inserts from a
sequence of 2-tuples, keeping a sequence number as a class
attribute instead of using len, etc.

Regards. Mel.