Python 元组

一、如何创建元组

>>> t = (1, 2, 3, 'root')
>>> t
(1, 2, 3, 'root')　

二、元组和列表的区别

• list是一种有序的集合，可以随时添加和删除其中的元素。
• 元祖也是一种有序列表，和list非常类似，不同点是tuple一旦定义了就不可修改，在一定意义上这也提高了代码的安全性，查询方法和list一样

>>> dir(a)
['append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']
>>> dir(t)
['count', 'index']　

>>> type(a)
<class 'list'>
>>> type(t)
<class 'tuple'>

class tuple(object):
    """
    tuple() -> empty tuple
    tuple(iterable) -> tuple initialized from iterable's items
    
    If the argument is a tuple, the return value is the same object.
    """
    def count(self, value): # real signature unknown; restored from __doc__
        """ T.count(value) -> integer -- return number of occurrences of value """
        return 0

    def index(self, value, start=None, stop=None): # real signature unknown; restored from __doc__
        """
        T.index(value, [start, [stop]]) -> integer -- return first index of value.
        Raises ValueError if the value is not present.
        """
        return 0

    def __add__(self, y): # real signature unknown; restored from __doc__
        """ x.__add__(y) <==> x+y """
        pass

    def __contains__(self, y): # real signature unknown; restored from __doc__
        """ x.__contains__(y) <==> y in x """
        pass

    def __eq__(self, y): # real signature unknown; restored from __doc__
        """ x.__eq__(y) <==> x==y """
        pass

    def __getattribute__(self, name): # real signature unknown; restored from __doc__
        """ x.__getattribute__('name') <==> x.name """
        pass

    def __getitem__(self, y): # real signature unknown; restored from __doc__
        """ x.__getitem__(y) <==> x[y] """
        pass

    def __getnewargs__(self, *args, **kwargs): # real signature unknown
        pass

    def __getslice__(self, i, j): # real signature unknown; restored from __doc__
        """
        x.__getslice__(i, j) <==> x[i:j]
                   
                   Use of negative indices is not supported.
        """
        pass

    def __ge__(self, y): # real signature unknown; restored from __doc__
        """ x.__ge__(y) <==> x>=y """
        pass

    def __gt__(self, y): # real signature unknown; restored from __doc__
        """ x.__gt__(y) <==> x>y """
        pass

    def __hash__(self): # real signature unknown; restored from __doc__
        """ x.__hash__() <==> hash(x) """
        pass

    def __init__(self, seq=()): # known special case of tuple.__init__
        """
        tuple() -> empty tuple
        tuple(iterable) -> tuple initialized from iterable's items
        
        If the argument is a tuple, the return value is the same object.
        # (copied from class doc)
        """
        pass

    def __iter__(self): # real signature unknown; restored from __doc__
        """ x.__iter__() <==> iter(x) """
        pass

    def __len__(self): # real signature unknown; restored from __doc__
        """ x.__len__() <==> len(x) """
        pass

    def __le__(self, y): # real signature unknown; restored from __doc__
        """ x.__le__(y) <==> x<=y """
        pass

    def __lt__(self, y): # real signature unknown; restored from __doc__
        """ x.__lt__(y) <==> x<y """
        pass

    def __mul__(self, n): # real signature unknown; restored from __doc__
        """ x.__mul__(n) <==> x*n """
        pass

    @staticmethod # known case of __new__
    def __new__(S, *more): # real signature unknown; restored from __doc__
        """ T.__new__(S, ...) -> a new object with type S, a subtype of T """
        pass

    def __ne__(self, y): # real signature unknown; restored from __doc__
        """ x.__ne__(y) <==> x!=y """
        pass

    def __repr__(self): # real signature unknown; restored from __doc__
        """ x.__repr__() <==> repr(x) """
        pass

    def __rmul__(self, n): # real signature unknown; restored from __doc__
        """ x.__rmul__(n) <==> n*x """
        pass

    def __sizeof__(self): # real signature unknown; restored from __doc__
        """ T.__sizeof__() -- size of T in memory, in bytes """
        pass

三、元组如何转换为列表

>>> list(t)
[1, 2, 3, 'root']　

四、可变的tuple

# 当元祖内部放一个列表的时候，这个元祖中的列表的值就可以变化了，实际上tuple并没有改变，变的是内部list的值

>>> m = (1, 'A', ['root', 'gm'])
>>> m
(1, 'A', ['root', 'gm'])

# 查看元组第３个元素的值

>>> m[2]
['root', 'gm']

# 其查询列表和元组的数据结构类似与C语言中的１维数组和２维数组

>>> m[2][1]
'gm'

# 修改原列表第２个元素的值

>>> m[2][1]='hlr'

# 查看元组m
>>> m
(1, 'A', ['root', 'hlr'])