参考：http://*.com/questions/2731111/python-lambdas-and-variable-bindings/2731175#2731175
代码:
1. 延迟绑定
class LateBindCounter(object):
def __init__(self):
self.func_map = {}
self.setitem = setitem
for i, key in enumerate([(0, 0), (0, 1), (1, 0), (1, 1)]):
self.func_map[key] = lambda x: setitem(x, i, x[i]+1)
def calc(self):
count = [0, 0, 0, 0, 0]
for k in (
(0, 1),
(1, 0),
(2, 3),
(4, 5),
(1, 0),
(0, 0)
):
inc_func = self.func_map.get(k, lambda x: setitem(x, -1, x[-1]+1))
inc_func(count)
print count
2. 默认值
class LateBindDefaultValueCounter(object):
def __init__(self):
self.func_map = {}
self.setitem = setitem
for i, key in enumerate([(0, 0), (0, 1), (1, 0), (1, 1)]):
self.func_map[key] = lambda x, i=i: setitem(x, i, x[i]+1)
def calc(self):
count = [0, 0, 0, 0, 0]
for k in (
(0, 1),
(1, 0),
(2, 3),
(4, 5),
(1, 0),
(0, 0)
):
inc_func = self.func_map.get(k, lambda x: setitem(x, -1, x[-1]+1))
inc_func(count)
print count
3. exec
class Counter(object):
def __init__(self):
self.func_map = {}
self.setitem = setitem
for i, key in enumerate([(0, 0), (0, 1), (1, 0), (1, 1)]):
exec 'func_map[%s] = lambda x: setitem(x, %s, x[%s]+1)' % (key, i, i) in self.__dict__
def calc(self):
count = [0, 0, 0, 0, 0]
for k in (
(0, 1),
(1, 0),
(2, 3),
(4, 5),
(1, 0),
(0, 0)
):
inc_func = self.func_map.get(k, lambda x: setitem(x, -1, x[-1]+1))
inc_func(count)
print count
4. 测试及结果
if __name__ == '__main__':
c = Counter()
c.calc() # [1, 1, 2, 0, 2]
lb = LateBindCounter()
lb.calc() # [0, 0, 0, 4, 2]
lbd = LateBindDefaultValueCounter()
lbd.calc() # [1, 1, 2, 0, 2]