Python数据类型详解（三）元祖：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 """
    （T.count(价值)- >整数,返回值的出现次数）
    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.
    """
    （T。指数(价值,[开始,[不要]])- >整数,返回第一索引值。提出了ValueError如果不存在的价值。）
    return 0

  def __add__(self, *args, **kwargs): # real signature unknown
    """ Return self+value. """
    pass

  def __contains__(self, *args, **kwargs): # real signature unknown
    """ Return key in self. """
    pass

  def __eq__(self, *args, **kwargs): # real signature unknown
    """ Return self==value. """
    pass

  def __getattribute__(self, *args, **kwargs): # real signature unknown
    """ Return getattr(self, name). """
    pass

  def __getitem__(self, *args, **kwargs): # real signature unknown
    """ Return self[key]. """
    pass

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

  def __ge__(self, *args, **kwargs): # real signature unknown
    """ Return self>=value. """
    pass

  def __gt__(self, *args, **kwargs): # real signature unknown
    """ Return self>value. """
    pass

  def __hash__(self, *args, **kwargs): # real signature unknown
    """ Return hash(self). """
    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, *args, **kwargs): # real signature unknown
    """ Implement iter(self). """
    pass

  def __len__(self, *args, **kwargs): # real signature unknown
    """ Return len(self). """
    pass

  def __le__(self, *args, **kwargs): # real signature unknown
    """ Return self<=value. """
    pass

  def __lt__(self, *args, **kwargs): # real signature unknown
    """ Return self

三.所有元祖数据类型举例

#count 用于计算元素出现的个数
name_tuple = ("zhangyanlin","suoning","nick")
print(name_tuple.count('zhangyanlin'))
 
#index获取指定元素的指定位置
name_tuple = ("zhangyanlin","suoning","nick")
print(name_tuple.index('zhangyanlin'))


四.索引

name_tuple = ("zhangyanlin","suoning","nick")
print(name_tuple[1])


五.切片

#取出第一位到最后一位减1的元素
name_tuple = ("zhangyanlin","suoning","nick")
print(name_tuple[0:len(name_tuple)-1])


六.总长度len

#取出最后一位减1的元素
name_tuple = ("zhangyanlin","suoning","nick")
print(name_tuple[len(name_tuple)-1])


七.for循环

name_tuple = ("zhangyanlin","suoning","nick")
for i in name_tuple:
  print(i)


那么使用 tuple 有什么好处呢？
Tuple 比 list 操作速度快。如果您定义了一个值的常量集，并且唯一要用它做的是不断地遍历它，请使用 tuple 代替 list。

如果对不需要修改的数据进行 “写保护”，可以使代码更安全。使用 tuple 而不是 list 如同拥有一个隐含的 assert 语句，说明这一数据是常量。如果必须要改变这些值，则需要执行 tuple 到 list 的转换 (需要使用一个特殊的函数)。


还记得我说过 dictionary keys 可以是字符串，整数和 “其它几种类型”吗？Tuples 就是这些类型之一。Tuples 可以在 dictionary 中被用做 key，但是 list 不行。实际上，事情要比这更复杂。Dictionary key 必须是不可变的。Tuple 本身是不可改变的，但是如果您有一个 list 的 tuple，那就认为是可变的了，用做 dictionary key 就是不安全的。只有字符串、整数或其它对 dictionary 安全的 tuple 才可以用作 dictionary key。


Tuples 可以用在字符串格式化中，我们会很快看到。
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