consider a file named lst.txt, which contents are:`('a', ('b',('c','d')))`,when read from it and try to convert to tuple, but it returns chars;

codes:

```
if __name__ == '__main__':
  with open('lst.txt') as fx:
    strs = fx.readline()
    print tuple(strs)

```

the result is: `['(', "'", 'a', "'", ',', '(', "'", 'b', "'", ',', '(', "'", 'c', "'", ',', "'",
 'd', "'", ')', ')', ')', '\n']`

but if I use the python shell, result is different: 

```
>>>test_str = ('a', ('b',('c','d')))
>>>result = tuple(test_str)
>>>print result
('a', ('b', ('c', 'd')))

```

why?