By changing a single line in the program of Example E8.1, output the 10 most accurately known constants (excluding those set to their values by definition).
Change the line
for rec in constants[:-10]:
to:
for rec in constants[constants['rel_unc'] > 0][:10]:
and the format specifier in the output line to ':g' (since the uncertainties are less than 1 ppm).
1.74797e-07 ppm: electron g factor = -2.00232
1.79792e-07 ppm: electron mag. mom. to Bohr magneton ratio = -1.00116
1.90811e-06 ppm: hertz-hartree relationship = 1.51983e-16 E_h
1.91096e-06 ppm: Rydberg constant times hc in eV = 13.6057 eV
...
The most accurately known constant is the electron $g$-factor.