test_is_float_int.py

#!/usr/bin/env python

import re
import fastnumbers

def is_int1(v):
    try:
        int(v)
        return True
    except ValueError:
        return False


def is_int2(v):
    return v.lstrip('+-').isdigit()


def is_float1(v):
    try:
        float(v)
        return True
    except:
        return False


_float_regexp = re.compile(r"^[-+]?(?:[Nn][Aa][Nn]|[Ii][Nn][Ff](?:[Ii][Nn][Ii][Tt][Yy])?|(?:\b[0-9]+(?:\.[0-9]*)?|\.[0-9]+)(?:[eE][-+]?[0-9]+\b)?)$").match

def is_float2(v):
    return True if _float_regexp(v) else False


def is_float3(v):
    return fastnumbers.isfloat(v)


def test_for_inputs(func, inputs):
    for s in inputs:
        func(s)


import timeit
import itertools

if __name__ == '__main__':
    number = 100000

    inputs = ["238764", "2", "sdkjhf", "4398265.238476"]
    exponents = ['', 'e3', 'e+3', 'e-3', 'e03', 'e+03', 'e-03', 'ee3']
    exponents += [ s.upper() for s in exponents ]
    inputs += [ ''.join(t) for t in list(itertools.product(['', '+', '-', '+-', '.'], ['', '1', '1.', '.1', '0x1', '..'], exponents)) ]
    special_values = ['Inf', 'NaN', 'Infinity', 'Infi']
    special_values += [ s.upper() for s in special_values ] + [ s.lower() for s in special_values ]
    inputs += [ ''.join(t) for t in list(itertools.product(['', '+', '-'], special_values)) ]

    # for func in ["is_int1", "is_int2", "is_float1", "is_float2", "is_float3"]:
    for func in ["is_float1", "is_float2", "is_float3"]:
        for s in inputs:
            print 'func=%s, input=%s, answer=%s' % (func, s, str( locals()[func](s) ))
        print 'func=%s, time=%f' % (func, timeit.timeit('test_for_inputs(%s, inputs)' % (func,), setup='from __main__ import %s, inputs, test_for_inputs' % (func,), number=number))

I commented out the is_int tests for my tests, as apparent in the gist.

Timing outputs on my machine:

func=is_float1, time=46.657828
func=is_float2, time=30.435496
func=is_float3, time=10.895729

Results agrees for all inputs between those three methods, except for the special values.