Check If Input Is a Number

MediumPython

Problem

Write a function that checks if the input is or is not a number.

Treat the input as a string and return True only for valid finite decimal or scientific-notation formats. Allow an optional leading sign, decimal values such as 12, -3.5, .8, and 7., and exponents such as 1e-4; reject whitespace, empty strings, malformed numbers, NaN, and infinity.

Input: one string value.

Output: a Boolean indicating whether value is a valid number.

Constraints

value is a string
0 <= len(value) <= 1000
Only ASCII decimal digits, signs, decimal points, and exponent markers are relevant
Leading or trailing whitespace is invalid

Function Signature

def is_number(value):

CodePython 3

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Run your code to see test output here.