The three logical operators not, and and or enable you to compose boolean expressions and by this way to construct more complex conditions. Here are some examples:
>>> seq = 'ATGCnATG' >>> 'n' in seq or 'N' in seq True >>> 'A' in seq and 'C' in seq True >>> 'n' not in seq False >>> len(seq) > 100 and 'n' not in seq False >>> not len(seq) > 100 True
The or operation is not an exclusive or as it is sometimes used in the current languages. An or expression is also true if both subexpressions are true.
>>> seq = 'ATGCnATG' >>> 'A' in seq or 'C' in seq True