Parse a float or return None

Summary

Convert strings to floats robustly and reject non-finite results.

Problem statement

Floating-point parsing using float(s) can produce special values like NaN or infinity. Implement parse_float(s) that attempts to convert s to a Python float. If conversion fails or the result is not a finite number (NaN or infinite), return None. The function should tolerate leading/trailing whitespace. It should not accept empty strings or None.

Task

Implement a parser that returns a float for valid numeric strings, otherwise returns None (including for NaN and infinities).

Examples

Input format

Call parse_float(s) where s is typically a string representing a number.

Output format

Return a float for valid finite numbers, otherwise return None.

Constraints

Reject NaN and infinities by returning None. Use math.isfinite to check finiteness. Do not accept non-string, non-numeric inputs silently; attempt to cast via float() and handle exceptions.

Samples