Create dict from two lists

[py]

I have two lists which I want to use to create a dictionary. List x
would be the keys, and list y is the values.

x = [1,2,3,4,5]
y = ['a','b','c','d','e']

Any suggestions? looking for an efficent simple way to do this...maybe
i am just having a brain fart...i feel like this is quit simple.

thanks.

[Diez B. Roggisch]

py wrote:

I have two lists which I want to use to create a dictionary. List x
would be the keys, and list y is the values.

x = [1,2,3,4,5]
y = ['a','b','c','d','e']

Any suggestions? looking for an efficent simple way to do this...maybe
i am just having a brain fart...i feel like this is quit simple.

dict(zip(x,y))

Diez

[Paul McGuire]

"py" <co*******@gmail.com> wrote in message
news:11**********************@o13g2000cwo.googlegr oups.com...

I have two lists which I want to use to create a dictionary. List x
would be the keys, and list y is the values.

x = [1,2,3,4,5]
y = ['a','b','c','d','e']

Any suggestions? looking for an efficent simple way to do this...maybe
i am just having a brain fart...i feel like this is quit simple.

thanks.

x = [1,2,3,4,5]
y = ['a','b','c','d','e']
dict(zip(x,y))

{1: 'a', 2: 'b', 3: 'c', 4: 'd', 5: 'e'}

-- Paul

[Carsten Haese]

On Fri, 2006-02-10 at 08:51, py wrote:

I have two lists which I want to use to create a dictionary. List x
would be the keys, and list y is the values.

x = [1,2,3,4,5]
y = ['a','b','c','d','e']

Any suggestions? looking for an efficent simple way to do this...maybe
i am just having a brain fart...i feel like this is quit simple.

d = dict(zip(x,y))

-Carsten

[Xavier Morel]

Diez B. Roggisch wrote:

py wrote:

I have two lists which I want to use to create a dictionary. List x
would be the keys, and list y is the values.

x = [1,2,3,4,5]
y = ['a','b','c','d','e']

Any suggestions? looking for an efficent simple way to do this...maybe
i am just having a brain fart...i feel like this is quit simple.

dict(zip(x,y))

Diez

I'd even suggest using izip (from itertools), it's often much faster
than zip (end result is the same).

Demo:

from itertools import izip
l1 = range(5000)
l2 = range(5000, 10000)
from timeit import Timer
t1 = Timer("dict(zip(l1, l2))", "from __main__ import l1, l2")
t2 = Timer("dict(izip(l1, l2))", "from __main__ import l1, l2, izip")
min(t1.repeat(5, 10000)) 17.989041903370406 min(t2.repeat(5, 10000)) 10.381146486494799

42% speed gain from using izip instead of zip (memory was not an issue
during the test, machine had 1.3Gb of available ram)

[py]

Thanks, itertools.izip and just zip work great. However, I should have
mentioned this, is that I need to keep the new dictionary sorted.

d = {1:'first', -5 : 'negative 5', 6:'six', 99:'ninety-nine',
3:'three'}
keys = d.keys()
keys.sort()
vals = map(d.get, keys)

At this point keys is sorted [-5, 1, 3, 6, 99] and vals is sorted
['negative 5', 'first', 'three', 'six', 'ninety-nine']

Using zip does not create the dictionary sorted in this order.
new_d = dict(zip(keys, vals))

How can I use the two lists, keys and vals to create a dictionary such
that the items keep their order?

Thanks.

[Iain King]

py wrote:

Thanks, itertools.izip and just zip work great. However, I should have
mentioned this, is that I need to keep the new dictionary sorted.

d = {1:'first', -5 : 'negative 5', 6:'six', 99:'ninety-nine',
3:'three'}
keys = d.keys()
keys.sort()
vals = map(d.get, keys)

At this point keys is sorted [-5, 1, 3, 6, 99] and vals is sorted
['negative 5', 'first', 'three', 'six', 'ninety-nine']

Using zip does not create the dictionary sorted in this order.
new_d = dict(zip(keys, vals))

How can I use the two lists, keys and vals to create a dictionary such
that the items keep their order?

Thanks.

Short answer - you can't. Dictionaries aren't sequential structures,
so they have no sorted form. You can iterate through it in a sorted
manner however, as long as you keep your list of keys:

keys.sort()
for k in keys:
print d[k]

Iain

[Mikael Olofsson]

py wrote:

Thanks, itertools.izip and just zip work great. However, I should have
mentioned this, is that I need to keep the new dictionary sorted.

Dictionaries aren't sorted. Period.

/MiO

[bearophileHUGS]

py:

Thanks, itertools.izip and just zip work great. However, I should have
mentioned this, is that I need to keep the new dictionary sorted.

A Python dictionary is an unsorted data structure, so you cannot have
it sorted as you please.
(I have seen that lot of people ask for a sorted dictionary and for
permutation/combination functions, maybe they are batteries to be
included too in the standard library.)
If you need an ordered dict you can manage it yourself, keeping the
lists of keys, etc, or you can use an ordered dict implementation:

http://www.voidspace.org.uk/python/odict.html
http://aspn.activestate.com/ASPN/Coo.../Recipe/438823
Etc.

Bye,
bearophile

[py]

Iain King wrote:

Short answer - you can't. Dictionaries aren't sequential structures,
so they have no sorted form. You can iterate through it in a sorted
manner however, as long as you keep your list of keys:

keys.sort()
for k in keys:
print d[k]

Iain

duh!....thanks.