Traling junk in string.atof (RE: array constructor)

Tim Peters tim_one at email.msn.com
Mon Feb 28 03:53:52 CET 2000


[Tom Holroyd]
> ...
> While I'm here, string.atof() and float() both barf on "123.45," while the
> C atof() doesn't.  A quick check of the code (stropmodule.c) shows that
> there is an explicit check for junk at the end of the string.

Right.

> Is there some reason for this besides just being annoying?  :-)

Yes, but simply because "123.45," does not match the syntax for "a number".
The trailing comma may be harmless, or it may indicate your program has
gotten lost, or that your data has gotten corrupted, or that your data was
ill-formed to begin with.  Python refuses to guess that it makes sense,
because it has no way to *know*, and guessing "ya, OK" errs in the wrong
direction (screws *you* the most).  Python takes this attitude all over the
place, btw -- string.atof is just one instance of it.

I'm curious how you ended up with a numeric string with a trailing comma to
begin with.  For example, if you're reading lines of comma-separated values,
the natural idiom is

    numbers = map(float, string.split(line, ","))

which gets rid of the commas explicitly.

> I vote to remove it.

I'll set up a web page to keep a running tally <wink>.

better-careful-coding-than-endless-debugging-ly y'rs  - tim






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