python 的函数内部变量不能和函数重名？

第一段错误的代码：
def test(i):
....if i == 0:
........test = 'one'
........print test
....elif i == 1:
........test = 'two'
........print test
....elif i == 2:
........test(1)
test(2)
我以为结果是'two'，
实际运行结果：UnboundLocalError: local variable 'test' referenced before assignment

==============================

第二段错误的代码：
def test(i):
....if i == 0:
........test = 'one'
........print test
....elif i == 1:
........test_1 = 'two'
........print test_1
....elif i == 2:
........test(1)
test(2)
我以为结果是'two'，
实际运行结果：UnboundLocalError: local variable 'test' referenced before assignment

==============================

第三段的代码：
def test(i):
....if i == 0:
........test_0 = 'one'
........print test_0
....elif i == 1:
........test_1 = 'two'
........print test_1
....elif i == 2:
........test(1)
test(2)
运行结果正确：'two'


谁能给我解释一下0.0
菜鸟实在被搞晕了