动态执行python代码

a = 1
exec "a = 2"
print a

name = "os"
exec "import %s"%name

class a():
    def one(self):
        print 1
    def two(self):
        print 2
    def what(self,num):
        eval('self.'+num+"()")

num = input()
A = a()
A.what(num)

class a():
    def one(self):
        print 1
    def two(self):
        print 2
num = input()
A = a()
if num == "one":
    A.one()
if num = "TWO":
    a.two()