lambda表达式是匿名函数，把它当作函数定义。
list = []
for i in range(1,4):
list.append(lambda:fuc(i))

def fuc(num):
return num * num
for l in list:
print(l())

打印结果为 9 9 9

list = []
for i in range(1,4):
list.append(lambda n = i:fuc(n))

def fuc(num):
return num * num
for l in list:
print(l())

打印结果为 1 4 9

参考
http://blog.chinaunix.net/uid-31134698-id-5747061.html