# Python中的operator模块 operator 模块提供了一套与Python的内置运算符对应的高效率函数。例如,operator.add(x, y) 与表达式 x+y 相同。 许多函数名与特殊方法名相同,只是没有双下划线。为了向后兼容性,也保留了许多包含双下划线的函数。为了表述清楚,建议使用没有双下划线的函数。 operator.attrgetter ``` python def attrgetter(*items): if any(not isinstance(item, str) for item in items): raise TypeError('attribute name must be a string') if len(items) == 1: attr = items[0] def g(obj): return resolve_attr(obj, attr) else: def g(obj): return tuple(resolve_attr(obj, attr) for attr in items) return g def resolve_attr(obj, attr): for name in attr.split("."): obj = getattr(obj, name) return obj ``` operator.itemgetter ``` python def itemgetter(*items): if len(items) == 1: item = items[0] def g(obj): return obj[item] else: def g(obj): return tuple(obj[item] for item in items) return g ``` examples ``` python >>> itemgetter(1)('ABCDEFG') 'B' >>> itemgetter(1,3,5)('ABCDEFG') ('B', 'D', 'F') >>> itemgetter(slice(2,None))('ABCDEFG') 'CDEFG' >>> soldier = dict(rank='captain', name='dotterbart') >>> itemgetter('rank')(soldier) 'captain' >>> inventory = [('apple', 3), ('banana', 2), ('pear', 5), ('orange', 1)] >>> getcount = itemgetter(1) >>> list(map(getcount, inventory)) [3, 2, 5, 1] >>> sorted(inventory, key=getcount) [('orange', 1), ('banana', 2), ('apple', 3), ('pear', 5)] ``` operator.methodcaller ``` python def methodcaller(name, *args, **kwargs): def caller(obj): return getattr(obj, name)(*args, **kwargs) return caller ``` 摘录自[官方文档中文版](https://docs.python.org/zh-cn/3/library/operator.html)