python 2.2 string conversion ?

Gary Herron gherron at islandtraining.com
Thu Jul 24 08:10:30 CEST 2003


>
> >>> x="e10ea210"
> >>> y=long(x)
>
> Traceback (most recent call last):
>   File "<pyshell#7>", line 1, in ?
>     y=long(x)
> ValueError: invalid literal for long(): e10ea210

> What am I doing wrong?

You didn't specify what you are trying to do here, but I'll make a
wild *guess* that the string in x is a hexadecimal (i.e., base 16)
value.  However, Python can't go around making such a guess, so you
have to explicitly specify your radix (radix being another term for
base) like this:

>>> print long("e10ea210",16)
3775832592

or tell it to infer the radix from a '0x' prefix:

>>> print long("0xe10ea210",0)
3775832592

Here are the relevant portions of the manual:

long(x[, radix])

  Convert a string or number to a long integer. If the argument is a
  string, it must contain a possibly signed number of arbitrary size,
  possibly embedded in whitespace; this behaves identical to
  string.atol(x). The radix argument is interpreted in the same way as
  for int(), and may only be given when x is a string. Otherwise, the
  argument may be a plain or long integer or a floating point number,
  and a long integer with the same value is returned. Conversion of
  floating point numbers to integers truncates (towards zero).


int(x[, radix])

  Convert a string or number to a plain integer. If the argument is a
  string, it must contain a possibly signed decimal number
  representable as a Python integer, possibly embedded in whitespace;
  this behaves identical to string.atoi(x[, radix]). The radix
  parameter gives the base for the conversion and may be any integer
  in the range [2, 36], or zero. If radix is zero, the proper radix is
  guessed based on the contents of string; the interpretation is the
  same as for integer literals. If radix is specified and x is not a
  string, TypeError is raised. Otherwise, the argument may be a plain
  or long integer or a floating point number. Conversion of floating
  point numbers to integers truncates (towards zero). If the argument
  is outside the integer range a long object will be returned instead.


Gary Herron







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