Increment a float with the smallest possible value

demo.py

import sys

for x in (0.0, 1/10, -1/10, sys.float_info.max, sys.float_info.min, float('inf'), float('-inf'), float('NaN')):
    print(f'{x}++ => {float_incr(x)}')

i, xi = 0, float('-inf')
while xi < float('inf'):
    x = float_incr(xi)
    assert x > xi
    xi = x / 2 if x < 0 else x * 2
    i += 1
    
print('\n', f'2**{i} floats')

demo_results.txt

0.0++ => 5e-324
0.1++ => 0.10000000000000002
-0.1++ => -0.09999999999999999
1.7976931348623157e+308++ => inf
2.2250738585072014e-308++ => 2.225073858507202e-308
inf++ => inf
-inf++ => -1.7976931348623157e+308
nan++ => nan

 2**4194 floats

float_increment.py

import struct


def float_incr(x: float):
    if x == float('inf') or x != x:
        # ignore infinite and NaN
        return x
        
    x_raw = struct.unpack('>Q', struct.pack('>d', x or 0))[0]
    dx_raw = 1 if x >= 0 else -1
    return struct.unpack('>d', struct.pack('>Q', x_raw + dx_raw))[0]