[Python-Dev] Re: Decimal data type issues (original) (raw)

Batista, Facundo FBatista at uniFON.com.ar
Tue Apr 20 09:28:48 EDT 2004

[Kevin Jacobs]

#- >[Jewett, Jim J] #- >#- Under the current implementation: #- >#- (0, (2, 4, 0, 0, 0), -4) #- >#- is not quite the same as #- >#- (0, (2, 4) -1) #- >#- Given this, is should be possible for the user to specify #- >#- (at creation) which is desired. #- > #- >It is posible: #- > #- >>>>Decimal('2.4000') #- >Decimal( (0, (2, 4, 0, 0, 0), -4) ) #- > #- >>>>Decimal('2.4') #- >Decimal( (0, (2, 4), -1) ) #- >
#- #- Great!. One of my previous posts #- specifically listed #- that I didn't want to have to pre-parse and reformulate #- string literals to #- achieve the desired precision and scale. The "external"

what? :p

I still don't understand why do you want that.

#- >If you construct using precision, and the precision is #- smaller than the #- >quantity of digits you provide, you'll get rounded, but if #- the precision is #- >greater than the quantity of digits you provide, you don't #- get filled with #- >zeros. #- #- Rounding is exactly what should be done if one exceeds the desired #- precision. Using #- less that the desired precision (i.e., not filling in zeros) #- may be okay #- for many applications. #- This is because any operations on the value will have to be #- performed #- with the precision #- defined in the decimal context. Thus, the results will be #- identical, #- other than that the #- Decimal instance may not store the maximum precision #- available by the #- schema.

If I don't misunderstand, you're saying that store additional zeroes is important to your future operations?

Let's make an example.

If I have '2.4000', I go into decimal and get:

Decimal('2.4000') Decimal( (0, (2, 4, 0, 0, 0), -4) )

If I have '2.4', I go into decimal and get:

Decimal('2.4') Decimal( (0, (2, 4), -1) )

Are you trying to say that you want Decimal to fill up that number with zeroes...

Decimal('2.4', scale=4) # behaviour don't intended, just an example Decimal( (0, (2, 4, 0, 0, 0), -4) )

...just to represent that you have that precision in your measurements and reflect that in future arithmetic operations?

If yes, I think that: a) '2.4' and '2.4000' will behaviour identically in future operations; b) why do you need to represent in the number the precision of your measurement?

. Facundo

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