Re: convert user input to Decimal objects using eval()?

2005-03-30 Thread Raymond Hettinger 
> > [Julian Hernandez Gomez]
> >> is there a "easy way" to make eval() convert all floating
> >> numbers to Decimal objects and return a Decimal?

[Raymond Hettinger]
> > from decimal import Decimal
> > import re
> >
> > number =
> > re.compile(r"((\b|(?=\W))(\d+(\.\d*)?|\.\d+)([eE][+-]?\d{1,3})?)")
> > deciexpr = lambda s: number.sub(r"Decimal('\1')", s)

[Terry Reedy]
> This is less obvious and more useful, to me, than some of the recipies in
> the new Cookbook.

Okay, we can fix that.  I've cleaned it up a bit and posted it on ASPN with
references, docs, and a doctest:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/393265


Raymond


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Re: convert user input to Decimal objects using eval()?

2005-03-29 Thread Terry Reedy 

"Raymond Hettinger" <[EMAIL PROTECTED]> wrote in message 
news:[EMAIL PROTECTED]
> [Julian Hernandez Gomez]
>> This is maybe a silly question, but...
>>
>> is there a "easy way" to make eval() convert all floating
>> numbers to Decimal objects and return a Decimal?
>
> from decimal import Decimal
> import re
>
> number = 
> re.compile(r"((\b|(?=\W))(\d+(\.\d*)?|\.\d+)([eE][+-]?\d{1,3})?)")
> deciexpr = lambda s: number.sub(r"Decimal('\1')", s)
>
> for s in ('1.0001+0.111',
>   '+21.3e-5*85-.1234/81.6',
>   '1.0/7'):
>print '%s\n  --> %r' % (s, eval(s))
>s = deciexpr(s)
>print '%s\n  --> %r\n' % (s, eval(s))
>
>
>
> """
> 1.0001+0.111
>  --> 1.
> Decimal('1.0001')+Decimal('0.111')
>  --> Decimal("1.")
>
> +21.3e-5*85-.1234/81.6
>  --> 0.016592745098039215
> +Decimal('21.3e-5')*Decimal('85')-Decimal('.1234')/Decimal('81.6')
>  --> Decimal("0.01659274509803921568627450980")
>
> 1.0/7
>  --> 0.14285714285714285
> Decimal('1.0')/Decimal('7')
>  --> Decimal("0.1428571428571428571428571429")

This is less obvious and more useful, to me, than some of the recipies in 
the new Cookbook.

TJR



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Re: convert user input to Decimal objects using eval()?

2005-03-29 Thread Julian Hernandez Gomez 
On Tuesday 29 March 2005 03:04, Raymond Hettinger wrote:
> from decimal import Decimal
> import re
>
> number = re.compile(r"((\b|(?=\W))(\d+(\.\d*)?|\.\d+)([eE][+-]?\d{1,3})?)")
> deciexpr = lambda s: number.sub(r"Decimal('\1')", s)
>
> for s in ('1.0001+0.111',
>    '+21.3e-5*85-.1234/81.6',
>    '1.0/7'):
>     print '%s\n  --> %r' % (s, eval(s))
>     s = deciexpr(s)
>     print '%s\n  --> %r\n' % (s, eval(s))

Wow!

Thank you so much!!!

now I can do my simple math function evaluator much more reliable !

Thanks again!

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Julián
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Re: convert user input to Decimal objects using eval()?

2005-03-29 Thread Raymond Hettinger 
[Julian Hernandez Gomez]
> This is maybe a silly question, but...
>
> is there a "easy way" to make eval() convert all floating
> numbers to Decimal objects and return a Decimal?

from decimal import Decimal
import re

number = re.compile(r"((\b|(?=\W))(\d+(\.\d*)?|\.\d+)([eE][+-]?\d{1,3})?)")
deciexpr = lambda s: number.sub(r"Decimal('\1')", s)

for s in ('1.0001+0.111',
   '+21.3e-5*85-.1234/81.6',
   '1.0/7'):
print '%s\n  --> %r' % (s, eval(s))
s = deciexpr(s)
print '%s\n  --> %r\n' % (s, eval(s))



"""
1.0001+0.111
  --> 1.
Decimal('1.0001')+Decimal('0.111')
  --> Decimal("1.")

+21.3e-5*85-.1234/81.6
  --> 0.016592745098039215
+Decimal('21.3e-5')*Decimal('85')-Decimal('.1234')/Decimal('81.6')
  --> Decimal("0.01659274509803921568627450980")

1.0/7
  --> 0.14285714285714285
Decimal('1.0')/Decimal('7')
  --> Decimal("0.1428571428571428571428571429")

"""

Raymond Hettinger


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Re: convert user input to Decimal objects using eval()?

2005-03-28 Thread Swaroop C H 
On Mon, 28 Mar 2005 12:03:24 -0500, Julian Hernandez Gomez
<[EMAIL PROTECTED]> wrote:
> is there a "easy way" to make eval() convert all floating numbers to Decimal
> objects and return a Decimal?
> eval('1.0001+0.111') --> convert each number to a Decimal object,
> perform the sum and obtain a Decimal object as a result?
> maybe a parser is needed, but eval() already do the job, but I need the
> precision that Decimal offers for numerical applications.

If you need the precision, why are you using strings instead of the
numbers directly?

Also, why not simply use Decimal('1.000') + Decimal('0.111') ?

-- 
Swaroop C H
Blog: http://www.swaroopch.info
Book: http://www.byteofpython.info
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convert user input to Decimal objects using eval()?

2005-03-28 Thread Julian Hernandez Gomez 
Hi !

This is maybe a silly question, but...

is there a "easy way" to make eval() convert all floating numbers to Decimal 
objects and return a Decimal?

for example:

eval('1.0001+0.111') --> convert each number to a Decimal object, 
perform the sum and obtain a Decimal object as a result?

maybe a parser is needed, but eval() already do the job, but I need the 
precision that Decimal offers for numerical applications.

Thanks in advance.

-- 
Julián
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