Steven D'Aprano wrote:
> On Sat, Oct 02, 2021 at 02:53:03AM -0000, Debashish Palit wrote:
> > There is no need of a three_way_flag - just use a conditional
> > expression instead of an if-elif-else block,
> > Of course you need a three way flag if your function returns a three way
> flag. It returns False for ints, True for floats, and None for anything
> else.
> So the caller needs to handle three cases:
> - your function returns True, so call float(s)
> - your function returns False, so call int(s)
> - your function returns None, so handle the string some other way.
> How else could you do it?
Using a conditional expression, we can code it like this:
num = float(s) if (c := s.isfloat()) else int(s) if c is False else 0 # any
default
Better still if we know its going to be a number, we can do -
num = float(s) if s.isfloat() else int(s)
> > str.isfloat uses the int() and float() functions,
> > Correct, which is why your function is wasteful and inefficient. If I
> call `isfloat('123')`, the function calls float, and throws the result
> away, so I have to call float *again*. So if people use this function,
> they are effectively doing:
> s = '123.0' # input is a string, from somewhere else
> float(s) # throw away the result
> num = float(s)
str.isfloat does more than just convert to float. Even if you are not
converting to a float, str.isfloat is a good check for a valid number. We can
simply do -
if s.isfloat() is not None: # valid int or float
...
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