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())
