Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #87404

Re: Odd ValueError using float

Show all headers | View raw

On Sat, Mar 14, 2015 at 1:33 PM, Paul Rubin <no.email@nospam.invalid> wrote:
> emile <emile@fenx.com> writes:
>> *** NameError: name 'val' is not defined
>> (Pdb) l
>> 139         try:
>> 140             val = round(float(decval),1)
>> 141         except:
>> 142             import pdb; pdb.set_trace()
>
> If 'float' or 'round' throw an exception, the assignment to 'val' never
> happens, so 'val' is undefined.  Try examining the value of 'decval' in
> the debugger to see what is making the conversion fail.

That's exactly what the OP did :) Trouble is, it didn't help, because
it sure looked as if decval was the string '4'. My best guess was -
and is - that it's not just a string. We're looking at an SQL
interface routine here, so it may be that there's a string subclass
that length-limits itself, on the assumption that it's going into a
fixed-length database field. Let's see if I can recreate the OP's
situation...

>>> def Char(maxlen):
    class CharN(str):
        def __repr__(self):
            return repr(self[:maxlen])
    CharN.__qualname__ = CharN.__name__ = "Char(%d)"%maxlen
    return CharN

>>> four = Char(1)('41.700000000000003')
>>> four
'4'
>>> int(four)
Traceback (most recent call last):
  File "<pyshell#28>", line 1, in <module>
    int(four)
ValueError: invalid literal for int() with base 10: '4'

... well, close. Anyway, a string subclass could probably do this by
accident somehow.

ChrisA

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Odd ValueError using float emile <emile@fenx.com> - 2015-03-13 15:10 -0700
  Re: Odd ValueError using float Paul Rubin <no.email@nospam.invalid> - 2015-03-13 19:33 -0700
    Re: Odd ValueError using float Chris Angelico <rosuav@gmail.com> - 2015-03-14 14:09 +1100
    Re: Odd ValueError using float emile <emile@fenx.com> - 2015-03-14 08:28 -0700
    Re: Odd ValueError using float Chris Angelico <rosuav@gmail.com> - 2015-03-15 02:52 +1100
    Re: Odd ValueError using float Peter Otten <__peter__@web.de> - 2015-03-14 17:08 +0100
    Re: Odd ValueError using float emile <emile@fenx.com> - 2015-03-14 10:08 -0700
    Re: Odd ValueError using float emile <emile@fenx.com> - 2015-03-14 10:17 -0700
    Re: Odd ValueError using float Peter Otten <__peter__@web.de> - 2015-03-14 19:24 +0100
    Re: Odd ValueError using float emile <emile@fenx.com> - 2015-03-14 13:01 -0700
    Re: Odd ValueError using float Peter Otten <__peter__@web.de> - 2015-03-15 15:01 +0100
    Re: Odd ValueError using float emile <emile@fenx.com> - 2015-03-17 13:48 -0700

csiph-web