How to extract a floating number from a string [duplicate]

Answer 1

Python docs has an answer that covers +/-, and exponent notation

scanf() Token      Regular Expression
%e, %E, %f, %g     [-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?
%i                 [-+]?(0[xX][\dA-Fa-f]+|0[0-7]*|\d+)

This regular expression does not support international formats where a comma is used as the separator character between the whole and fractional part (3,14159). In that case, replace all \. with [.,] in the above float regex.

                        Regular Expression
International float     [-+]?(\d+([.,]\d*)?|[.,]\d+)([eE][-+]?\d+)?