Python之operator库

operator库常用方法

Function	Syntax
add(a+b)	a + b
concat(seq1,seq2)	seq1 + seq2
contains(seq, obj)	obj in seq
div(a,b)(without future.division)	a/b
truediv(a,b)(with future.division)	a/b
floordiv(a,b)	a // b
and_(a,b)	a & b
xor(a, b)	a ^ b
invert(a)	~a
or_(a, b)	a b
pow(a,b)	a ** b
is_(a,b)	a is b
is_not(a,b)	a is not b
setitem(obj, k, v)	obj[k] = val
delitem(obj, k)	del obj[k]
getitem(obj, k)	obj[k]
lshift(a,b)	a << b
mod(a,b)	a % b
mul(a,b)	a * b
neg(a)	-a
not_(a)	not a
pos(a)	+ a
rshift(a, b)	a >> b
repeat(seq,i)	seq * i
setitem(seq, slice(i,j),values)	seq[i,j] =values
delitem(seq,slice(i,j),values)	del seq[i,j]
getitem(seq, slice(i,j))	seq[i:j]
mod(s, obj)	s % obj
sub(a, b)	a-b
truth(obj)	obj

operator.itemgetter

　　返回一个可调用对象，获取项目使用的操作数的__getitem__()方法操作数。如果指定了多个项，则返回一个查找值元组。

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

>>> itemgetter(1)('ABCDEFG')
'B'
>>> itemgetter(1,3,5)('ABCDEFG')
('B', 'D', 'F')
>>> itemgetter(slice(2,None))('ABCDEFG')
'CDEFG'

operator.attrgetter

　　返回一个可调用对象,通过其操作数获取属性。如果请求多个属性，则返回一个属性元组。属性名称也可以包含点。

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