Re: dictionary: sorting the values preserving the order

[Satchidanand Haridas]

Rakesh wrote:
Hi,
 For a particular problem of mine, I want to sort key, value pairs
by its value.
Eg:
Input:
A, 4
B, 5
C, 1
D, 2
E, 3
I would like the output to be:
C
D
E
A
B
 

the following code does that:
 d1 = {'a':4,'b':5,'c':1,'d':2,'e':3}
 i1 = [ (d1[i], i) for i in d1.keys() ]
 i1.sort()
 i1
[(1, 'c'), (2, 'd'), (3, 'e'), (4, 'a'), (5, 'b')]
 for each in i1:
... print each[1]  
c
d
e
a
b

thanks,
Satchit


i.e. I would like to get the keys in the sorted order of values.
I did google around a little bit. One solution to a similar problem
suggested is:
# Courtesy:
http://aspn.activestate.com/ASPN/Python/Cookbook/Recipe/52306
def sortedDictValues3(adict):
   keys = adict.keys()
   keys.sort()
   return map(adict.get, keys)
This gets a list sorted by the keys. How would I get a revised
dictionary 
sorted by its values.

 

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Re: dictionary: sorting the values preserving the order

[Ron_Adam]

On 31 Mar 2005 22:40:53 -0800, Rakesh [EMAIL PROTECTED]
wrote:

Hi,
  For a particular problem of mine, I want to sort key, value pairs
by its value.

Eg:

Input:

A, 4
B, 5
C, 1
D, 2
E, 3

I would like the output to be:

C
D
E
A
B

i.e. I would like to get the keys in the sorted order of values.

Generally, dictionaries nearly always have two parts. The dictionary
itself, and a separate list of keys to access it with.  

To access the dictionary in a particular order, you just need a sorted
key list.

Since what you want is to access by value, you need to create a second
dictionary with the values as the keys.  That will only work if the
values never repeat. If they do, then you need to use a list and not a
dictionary.

This creates a second dictionary with a sorted value key list.

alpha_dict = {'A':4, 'B':5, 'C':1, 'D':2, 'E':3}

# Create a new dictionary with keys and values exchanged.
num_dict = {}
for k in alpha_dict.keys():
num_dict[ alpha_dict[k] ] = k

# Get the num_dict keys and sort them.
num_keys = num_dict.keys()
num_keys.sort()


Ron

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Re: dictionary: sorting the values preserving the order

[Luis M. Gonzalez]

Another alternative:

d1 = {'a':4,'b':5,'c':1,'d':2,'e':3­}

il=[(v,k) for k,v in d1.items()]
il.sort()

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Re: dictionary: sorting the values preserving the order

[Terry Reedy]

Rakesh [EMAIL PROTECTED] wrote in message 
news:[EMAIL PROTECTED]
 This gets a list sorted by the keys.

That is all you *can* get (with the list keys being the dict values).

 How would I get a revised dictionary sorted by its values.

You can't.  A dictionary is not sorted.  The print order is arbitrary and 
not controllable.

Terry J. Reedy



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dictionary: sorting the values preserving the order

[Rakesh]

Hi,
  For a particular problem of mine, I want to sort key, value pairs
by its value.

Eg:

Input:

A, 4
B, 5
C, 1
D, 2
E, 3

I would like the output to be:

C
D
E
A
B

i.e. I would like to get the keys in the sorted order of values.

I did google around a little bit. One solution to a similar problem
suggested is:

# Courtesy:
http://aspn.activestate.com/ASPN/Python/Cookbook/Recipe/52306
def sortedDictValues3(adict):
keys = adict.keys()
keys.sort()
return map(adict.get, keys)

This gets a list sorted by the keys. How would I get a revised
dictionary 
sorted by its values.

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Re: dictionary: sorting the values preserving the order

[Vikram]

hi,

assuming your key-value relationship is one-to-one then as a simple first
pass you can simply initialize d1={} and for i in d.keys(): d1[d[i]] = i
and pass d1 to your sortedDictValue3 function, no?

thanks,
Vikram


On 31 Mar 2005, Rakesh wrote:

 Hi,
   For a particular problem of mine, I want to sort key, value pairs
 by its value.

 Eg:

 Input:

 A, 4
 B, 5
 C, 1
 D, 2
 E, 3

 I would like the output to be:

 C
 D
 E
 A
 B

 i.e. I would like to get the keys in the sorted order of values.

 I did google around a little bit. One solution to a similar problem
 suggested is:

 # Courtesy:
 http://aspn.activestate.com/ASPN/Python/Cookbook/Recipe/52306
 def sortedDictValues3(adict):
 keys = adict.keys()
 keys.sort()
 return map(adict.get, keys)

 This gets a list sorted by the keys. How would I get a revised
 dictionary
 sorted by its values.



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