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('1.00000001+0.1111111') --> 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 4 3864
[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 ('1.00000001+0.1111111',
'+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))
"""
1.00000001+0.1111111
--> 1.11111111
Decimal('1.00000001')+Decimal('0.1111111')
--> Decimal("1.11111111")
+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
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 ('1.00000001+0.1111111', * *'+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!
--
Julián
"Raymond Hettinger" <vz******@verizon.net> wrote in message
news:6_72e.50077$u76.2569@trndny08... [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 ('1.00000001+0.1111111', '+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)) """ 1.00000001+0.1111111 --> 1.11111111 Decimal('1.00000001')+Decimal('0.1111111') --> Decimal("1.11111111")
+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
> > [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/Coo.../Recipe/393265
Raymond This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
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