None Exception rasied in try except block

Question

I use a simple function:

def is_float(value):
    try:
        float(value) #float(value if value else "")
        return True
    except ValueError:
        return False

to check if an value is float or not.
Now, even though the check is in an try except block, this error is raised if the value is None:

2023-02-06 09:47:27,021 app - ERROR:Exception ....
TypeError: float() argument must be a string or a number, not 'NoneType'.

Can someone explain why?
If you want to try it yourself, just execute the function with a None value and it will throw.

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Answer 1

Option #1: Use Exception clause (broadest) instead to handle the None type.

def is_float(value):
    try:
        float(value)
        return True
    except Exception:
        return False

Option #2: except the errors that you expect.

def is_float(value):
    try:
        float(value)
        return True
    except (TypeError, ValueError):
        return False

Tests:

assert is_float(1.2)
assert is_float(3)
assert is_float(0)
assert not is_float(None)

Answered By: rv.kvetch

Answer 2

Ah okay, nvm, I just saw my mistake.

except Exception as e:

would be what I wanted.
That was silly.

Answered By: user3793935

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