Replace x by float(x) if and only if it is not None

Question

x is either a string or None (for example a query param from a HTTP request: request.query.get('x')).

I’d like to transform it into a float if not None.

These 3 solutions work:

if x is None:
    y = None
else:
    y = float(x)

y = float(x) if x is not None else None    # or y = float(x) if x is not None else x

y = None if x is None else float(x)        # or y = x if x is None else float(x)

but probably is there a simpler way than this repetition of None?

Asked By: Basj

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Source

Answer 1

You can do it this way:

>>> x = "1.23"
>>> y = x and float(x)
>>> y
1.23
>>> x = None
>>> y = x and float(x)
>>> y

Answered By: sj95126

Answer 2

Yes, using exception handling. This handles empty string (ValueError) and when x == None (TypeError).

try:
    y = float(x)
except Exception:
    y = None

Answered By: Filip Hanes

Replace x by float(x) if and only if it is not None

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