In his Wisdom Of The Crowd article Joseph Buchdahl describes three different methods to remove the overround (also called ‘margin’ in the UK or ‘vig’ in the US) from bookmaker odds.

In many papers the logarithmic function is considered most accurate.

You can download a python script here oddsmath.py

Usage:

print(get_no_vig_odds_multiway(odds=[1.41, 4.2, 6.4, 22]))

Output: (1.492, 5.324, 8.697, 36.659)