I agree - the three builtin methods are almost the same (not sure if
there is any difference at all), while there is no trivial way to check for
a valid
float, or otherwise a chosen representation of a decimal number without
resorting
to a try-except statement, or complicated verification schemes that have
to deal with a lot of corner cases.
For validity one has to check if there are only digits - and decimal points
-
and the "-" unary sign. What if there is more of a "." in the string?
what if the "-" is not the first character?
And besides validity checking, there are also validity choices:
What if an unary "+" is present? Whitespace ok? "_" as digit separator ok?
scientific exponential notation accepted? What about Inf and Nan literals?
What about taking into account the locale setting?
But maybe, instead of yet another str method, a "parsefloat" function
that could get arguments and sensitive defaults for some choices -
it could live in "math" or "numbers".
I think it would be preferable than, say, adding a lot of options
to the `float` constructor. These are the options I can think
of the top of my mind:
```python
def parsefloat(
input: str,
/, *,
unary_minus: Bool = True,
unary_plus: Bool = False,
exponential: Bool = False,
inf_literal: Bool = False,
nan_literal: Bool = False,
whitespace: Bool = False,
use_locale: Bool = False,
digit_separators: Bool = False,
base: int = 10 (?),
decimal_places: Optional[int]=None(?),
enforce_decimal_places: Bool = False(?),
raise_on_error: Bool = False(?),
...) -> Tuple[Bool, float]:
...
```
The return value would consitss of a boolean, where True would indicate
success, and then the number.
Or it could return a single float, returning a NaN in case of parsing error.
this is simple callable - but it could be built on top of
a class that could take the configurations and parse
more than one number - it would be fit as a float parser
to be supplied for tasks like Json decoding, or
converting values in a Pandas Series.
On Sun, 27 Dec 2020 at 14:12, Tushar Sadhwani <tushar.sadhwani...@gmail.com>
wrote:
> str currently has methods like isdecimal, isnumeric and isdigit, but there
> isn't an isfloat check, which could be very handy.
>
> a trivial implementation could be as simple as:
>
> try:
> float(self)
> return True
> except ValueError:
> return False
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