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Initialise dictionary of dictionary

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  Initialise dictionary of dictionary Ayushi Dalmia <ayushidalmia2604@gmail.com> - 2014-01-23 07:15 -0800
    Re: Initialise dictionary of dictionary Tim Chase <python.list@tim.thechases.com> - 2014-01-23 09:30 -0600
      Re: Initialise dictionary of dictionary Ayushi Dalmia <ayushidalmia2604@gmail.com> - 2014-01-23 21:42 -0800
    Re:Initialise dictionary of dictionary Dave Angel <davea@davea.name> - 2014-01-23 10:34 -0500
    Re: Initialise dictionary of dictionary Tim Chase <python.list@tim.thechases.com> - 2014-01-23 09:41 -0600

#64615 — Initialise dictionary of dictionary

I need to initialise a dictionary of dictionary with float values. I do not know the size of the dictionary beforehand. How can we do that in Python

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#64617

On 2014-01-23 07:15, Ayushi Dalmia wrote:
> I need to initialise a dictionary of dictionary with float values.
> I do not know the size of the dictionary beforehand. How can we do
> that in Python --
 
Either

  d = {}

or, if you want

  from collections import defaultdict
  d = defaultdict(float)
  print(d["Hello"])

If you really do want a dict-of-dict that defaults to floats, you can
do

  d = defaultdict(lambda: defaultdict(float))
  print(d[3141]["Hello"])

-tkc

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#64661

Thank you so much Tim. This is precisely what I wanted to do! 

On Thursday, January 23, 2014 9:00:23 PM UTC+5:30, Tim Chase wrote:
> On 2014-01-23 07:15, Ayushi Dalmia wrote:
> 
> > I need to initialise a dictionary of dictionary with float values.
> 
> > I do not know the size of the dictionary beforehand. How can we do
> 
> > that in Python --
> 
>  
> 
> Either
> 
> 
> 
>   d = {}
> 
> 
> 
> or, if you want
> 
> 
> 
>   from collections import defaultdict
> 
>   d = defaultdict(float)
> 
>   print(d["Hello"])
> 
> 
> 
> If you really do want a dict-of-dict that defaults to floats, you can
> 
> do
> 
> 
> 
>   d = defaultdict(lambda: defaultdict(float))
> 
>   print(d[3141]["Hello"])
> 
> 
> 
> -tkc

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#64618

 Ayushi Dalmia <ayushidalmia2604@gmail.com> Wrote in message:
> I need to initialise a dictionary of dictionary with float values. I do not know the size of the dictionary beforehand. How can we do that in Python
> 

Do what?  There's no concept of pre-initializing a dictionary, and
 there's no specific limit to its eventual size.

Unsure of what the floats have to do with it. Perhaps you meant
 float KEYS. 

-- 
DaveA

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#64619

On 2014-01-23 10:34, Dave Angel wrote:
> Unsure of what the floats have to do with it. Perhaps you meant
>  float KEYS. 

using floats for keys can be dangerous, as small rounding errors in
math can produce keys different enough that they're not found by an
exact-match lookup.  But yeah, the original problem specification was
rather wanting in detail.  I tried my best at interpreting it, for
whatever that may be worth.

-tkc

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