[Python-bugs-list] [ python-Bugs-721171 ] Tkinter precision loss for doubles

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Bugs item #721171, was opened at 2003-04-14 11:32
Message generated for change (Comment added) made by gvanrossum
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https://sourceforge.net/tracker/?func=detail&atid=105470&aid=721171&group_id=5470

Category: Tkinter
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Tim Peters (tim_one)
Assigned to: Martin v. Löwis (loewis)
Summary: Tkinter precision loss for doubles

Initial Comment:
DoubleVar.set() (I think) goes thru PyObject_Str(), 
causing precision loss for doubles:

>>> import Tkinter
>>> import math
>>> x = Tkinter.DoubleVar(Tkinter.Tk())
>>> x.set(math.pi)
>>> x.get()
3.1415926535900001   # not good
>>> math.pi
3.1415926535897931   # original precision
>>> eval(str(math.pi))
3.1415926535900001   # reproduces Tk result
>>>

Reported on c.l.py.  Guido says you may know how to 
create a "native" Tcl/Tk double in this case instead.

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>Comment By: Guido van Rossum (gvanrossum)
Date: 2003-04-14 11:45

Message:
Logged In: YES 
user_id=6380

If a proper fix using Tcl float/double objects doesn't work
for some reason, maybe the attached fix (_tkinter.fix) would
work?

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You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=721171&group_id=5470