strings (dollar.cents) into floats

[Marshall T. Vandegrift]

luca bertini <luca.bertini at email.it> writes:

> i have strings which look like money values (ie 34.45)
> is there a way to convert them into float variables?
> everytime i try I get this error: "numb = float(my_line) ValueError:  
> empty string for float()"
> "

You actually have problems here -- the immediate, and the one which will
get you later :-).  First, that error message indicates that you passed
an empty string to `float()`:

    >>> float("")
    Traceback (most recent call last):
      File "<stdin>", line 1, in ?
    ValueError: empty string for float()

Second, if you the values your script is handling are actually monetary
values, you really don't want to represent them with `float`s anyway:

    >>> float("34.45")
    34.450000000000003

Binary floating point values are necessarily inexact.  I'm not 100% sure
what the best-practices are for representing monetary values in Python,
but the `decimal` module is probably a good start.

HTH,

-Marshall