sorting dictionary keys?

[John Smith]

Hi, what's the fastest way (least amount of typing) to sort dictionary
objects by the key? What's the fastest way of iterating over sorted keys
for a dictionary in terms of performance? Are the two equivalent?

The way I have been doing it is:

d = {}
#populate d
keys = d.keys()
keys.sort()
for k in keys:
print k, d[k]

but I would like to do:
#error here
for k in d.keys().sort():
print k, d[k]

why doesn't the nested function call work? Thanks in advance.

 

[Jay O'Connor]

> Hi, what's the fastest way (least amount of typing)

Never good criteria

but I would like to do:
#error here
for k in d.keys().sort():
print k, d[k]

why doesn't the nested function call work? Thanks in advance.

sort() sorts in place and returns None

 

[Emile van Sebille]

John Smith

Hi, what's the fastest way (least amount of typing) to sort dictionary
objects by the key? What's the fastest way of iterating over sorted keys
for a dictionary in terms of performance? Are the two equivalent?

The way I have been doing it is:

d = {}
#populate d
keys = d.keys()
keys.sort()
for k in keys:
print k, d[k]

but I would like to do:
#error here
for k in d.keys().sort():

sort sorts in place and doesn't return anything. In 2.4 you'll have
the sorted method.

print k, d[k]

why doesn't the nested function call work? Thanks in advance.

The shortest thing to type? You're there with s = d.keys() and
s.sort().

 

[Bruno Desthuilliers]

Hi, what's the fastest way (least amount of typing)

Never good criteria

but I would like to do:
#error here
for k in d.keys().sort():
print k, d[k]

why doesn't the nested function call work? Thanks in advance.

sort() sorts in place and returns None

<rant>
Which is one of the main PITA in Python IMHO
(not the fact that it sort in place, the fact that it does not return self).
</rant>

Bruno

 

[Serge Orlov]

<rant>
Which is one of the main PITA in Python IMHO
(not the fact that it sort in place, the fact that it does not return self).
</rant>

<hint>
def sort(lst):
lst.sort()
return lst
</hint>

-- Serge

 

[Jay O'Connor]

Hi, what's the fastest way (least amount of typing)

Never good criteria

but I would like to do:
#error here
for k in d.keys().sort():
print k, d[k]

why doesn't the nested function call work? Thanks in advance.

sort() sorts in place and returns None

<rant>
Which is one of the main PITA in Python IMHO
(not the fact that it sort in place, the fact that it does not return
self).
</rant>

Arguably, if that's a main PITA, that's not too bad. I like Python, but
there are other things about it that bug me more. It's a minor
annoyance and given the name, I think it makes sense. If it returned
itself or a copy, the name should probably be sorted()

 

[Bruno Desthuilliers]

<hint>
def sort(lst):
lst.sort()
return lst
</hint>

Which is pretty ugly and adds a useless function call.

I just can't understand *why* the BDFL made this choice.

 

[Peter Hansen]

Which is pretty ugly and adds a useless function call.

I just can't understand *why* the BDFL made this choice.

What part of the many past repetitions of the reason didn't
you understand?

-Peter

 

[Raymond Hettinger]

sort() sorts in place and returns None

<rant>
Which is one of the main PITA in Python IMHO
(not the fact that it sort in place, the fact that it does not return self).
</rant>

Bruno

Wish granted!

Py2.4 will have a classmethod called list.sorted() that accepts any
iterable as an argument and returns a new sorted list as a result.
It can be used anywhere you can use an expression (function call
arguments, lambdas, list comps, etc).


Raymond Hettinger

 

[Paul Rubin]

Py2.4 will have a classmethod called list.sorted() that accepts any
iterable as an argument and returns a new sorted list as a result.
It can be used anywhere you can use an expression (function call
arguments, lambdas, list comps, etc).

Oh cool, although it means allocating more memory for the new list.

 

[Serge Orlov]

Which is pretty ugly and adds a useless function call.

Why ugly? It adds the functionality you asked for, it doesn't
use any magic, it's readable. I have goodies.py module for
personal stuff like that.

I just can't understand *why* the BDFL made this choice.

The answer is the FAQ section of the Python web site.

-- Serge.

 

[Kristian Ovaska]

Hi, what's the fastest way (least amount of typing) to sort dictionary
objects by the key?

You could use a custom dictionary that does what you want.

class Mydict(dict):
def sortedkeys(self):
k = self.keys()
k.sort()
return k