Add .isfloat() method to str

[JimmyCarlos]

BPO	43808
Nosy	@ericvsmith, @JimmyCarlos

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-04-11.17:46:54.555>
created_at = <Date 2021-04-11.14:53:35.453>
labels = ['interpreter-core', 'type-feature', '3.10']
title = 'Add .isfloat() method to str'
updated_at = <Date 2021-04-11.17:46:54.555>
user = 'https://github.com/JimmyCarlos'

bugs.python.org fields:

activity = <Date 2021-04-11.17:46:54.555>
actor = 'gregory.p.smith'
assignee = 'none'
closed = True
closed_date = <Date 2021-04-11.17:46:54.555>
closer = 'gregory.p.smith'
components = ['Interpreter Core']
creation = <Date 2021-04-11.14:53:35.453>
creator = 'JimmyCarlos'
dependencies = []
files = []
hgrepos = []
issue_num = 43808
keywords = []
message_count = 2.0
messages = ['390785', '390789']
nosy_count = 2.0
nosy_names = ['eric.smith', 'JimmyCarlos']
pr_nums = []
priority = 'normal'
resolution = 'rejected'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue43808'
versions = ['Python 3.10']

[JimmyCarlos]

Hello Python Community!

One feature I think would be helpful would be a method to see if a str can be safely converted into a float. Currently, this is not doable without a long regex or a try-except block, as numbers like "-3.52" contain non-numeric symbols.

My suggestion is to make a new boolean method on the str class. Code-wise, it would behave quite similarly to this code:

def isfloat(s:str) -> bool:
    try:
        float(s)
        return True
    except:
        return False

I appreciate your feedback, so what do you all think?

[ericvsmith]

Wouldn't the next thing you do be to convert it to a float, so you'd call float() twice? I think you'd be better off just catching the exception yourself, and using the result of float().

I'm opposed to such a simple function being a member of str or in the stdlib. In all of my years using Python with plenty of floats, I've never needed this function.

The usual suggestion with such short functions it to just add them to your own utility library.