Python-12 序列

1、列表、元组、字符串的共同特点

-都可以通过索引得到每一个元素

-默认索引值总是从0开始

-可以通过分片的方法得到一个范围内的元素集合

-有很多共同的操作符（重复操作符、拼接操作符、成员关系操作符）

2、序列的常见BIF（内置方法）

-list(iterable) 

    把一个可迭代的对象转换为列表

    帮助文档

>>> help(list)
Help on class list in module builtins:

class list(object)
 |  list() -> new empty list
 |  list(iterable) -> new list initialized from iterable's items
 |  
 |  Methods defined here:
 |  
 |  __add__(self, value, /)
 |      Return self+value.
 |  
 |  __contains__(self, key, /)
 |      Return key in self.
 |  
 |  __delitem__(self, key, /)
 |      Delete self[key].
 |  
 |  __eq__(self, value, /)
 |      Return self==value.
 |  
 |  __ge__(self, value, /)
 |      Return self>=value.
 |  
 |  __getattribute__(self, name, /)
 |      Return getattr(self, name).
 |  
 |  __getitem__(...)
 |      x.__getitem__(y) <==> x[y]
 |  
 |  __gt__(self, value, /)
 |      Return self>value.
 |  
 |  __iadd__(self, value, /)
 |      Implement self+=value.
 |  
 |  __imul__(self, value, /)
 |      Implement self*=value.
 |  
 |  __init__(self, /, *args, **kwargs)
 |      Initialize self.  See help(type(self)) for accurate signature.
 |  
 |  __iter__(self, /)
 |      Implement iter(self).
 |  
 |  __le__(self, value, /)
 |      Return self<=value.
 |  
 |  __len__(self, /)
 |      Return len(self).
 |  
 |  __lt__(self, value, /)
 |      Return self<value.
 |  
 |  __mul__(self, value, /)
 |      Return self*value.n
 |  
 |  __ne__(self, value, /)
 |      Return self!=value.
 |  
 |  __new__(*args, **kwargs) from builtins.type
 |      Create and return a new object.  See help(type) for accurate signature.
 |  
 |  __repr__(self, /)
 |      Return repr(self).
 |  
 |  __reversed__(...)
 |      L.__reversed__() -- return a reverse iterator over the list
 |  
 |  __rmul__(self, value, /)
 |      Return self*value.
 |  
 |  __setitem__(self, key, value, /)
 |      Set self[key] to value.
 |  
 |  __sizeof__(...)
 |      L.__sizeof__() -- size of L in memory, in bytes
 |  
 |  append(...)
 |      L.append(object) -> None -- append object to end
 |  
 |  clear(...)
 |      L.clear() -> None -- remove all items from L
 |  
 |  copy(...)
 |      L.copy() -> list -- a shallow copy of L
 |  
 |  count(...)
 |      L.count(value) -> integer -- return number of occurrences of value
 |  
 |  extend(...)
 |      L.extend(iterable) -> None -- extend list by appending elements from the iterable
 |  
 |  index(...)
 |      L.index(value, [start, [stop]]) -> integer -- return first index of value.
 |      Raises ValueError if the value is not present.
 |  
 |  insert(...)
 |      L.insert(index, object) -- insert object before index
 |  
 |  pop(...)
 |      L.pop([index]) -> item -- remove and return item at index (default last).
 |      Raises IndexError if list is empty or index is out of range.
 |  
 |  remove(...)
 |      L.remove(value) -> None -- remove first occurrence of value.
 |      Raises ValueError if the value is not present.
 |  
 |  reverse(...)
 |      L.reverse() -- reverse *IN PLACE*
 |  
 |  sort(...)
 |      L.sort(key=None, reverse=False) -> None -- stable sort *IN PLACE*
 |  
 |  ----------------------------------------------------------------------
 |  Data and other attributes defined here:
 |  
 |  __hash__ = None

>>> 

空列表

字符串 迭代成一个列表

>>> a=list()
>>> a
[]
>>> b='beijing'
>>> b=list(b)
>>> b
['b', 'e', 'i', 'j', 'i', 'n', 'g']
>>> 

元组 迭代成一个列表

>>> c = (1,1,2,3,5,8,13,21,34)
>>> c = list(c)
>>> c
[1, 1, 2, 3, 5, 8, 13, 21, 34]
>>> 

  -tuple([iterable])

把一个可迭代对象转换为元组

空元组

字符串 ->元组

列表 -> 元组

>>> a = tuple()
>>> a
()
>>> a = 'beijing'
>>> a = tuple(a)
>>> a
('b', 'e', 'i', 'j', 'i', 'n', 'g')
>>> b = ['beijing']
>>> b = tuple(b)
>>> b
('beijing',)
>>> b[0]
'beijing'

-str(obj)

把obj对象转换为字符串

>>> a = (1,1,2,3,5)
>>> a = str(a)
>>> a
'(1, 1, 2, 3, 5)'
>>> len(a)
15
>>> num = [1,1,2,3,5,8]
>>> sum(num)
20
>>> for i in a:
	print(i)

	
(
1
,
 
1
,
 
2
,
 
3
,
 
5
)
>>> 

-len(sub)

返回sub的长度

-max()

返回序列或参数集合中的最大值

>>> max(1,3,5,2)
5
>>> max([1,4,2,7,3]) #列表
7
>>> max('1,7,2,9,4,6,4')
'9'
>>> max((1,7,2,9,4,6,4)) #元组
9
>>> 
>>> b = 'beijing'
>>> b = list(b)
>>> b
['b', 'e', 'i', 'j', 'i', 'n', 'g']
>>> max(b)
'n'
>>> #ascii码

-min()

返回序列或参数集合中的最小值

>>> b = 'beijing'
>>> b = list(b)
>>> b
['b', 'e', 'i', 'j', 'i', 'n', 'g']
>>> min(1,3,5,-2)
-2
>>> min([1,4,2,7,-3])
-3
>>> min('1,7,-2,9,4,6,4')
','
>>> min(b)
'b'
>>> 
>>> num = '1234567890'
>>> min(num)
'0'
>>> 

-sum(iterable[,start=0])

返回序列iterable和可选参数start的总和

>>> num = [1,1,2,3,5,8]
>>> sum(num)
20
>>> tuple1 = (1.2,4.5,2.6)
>>> sum(tuple1)
8.3
>>> sum(tuple1,1.1)
9.4
>>> 

-sorted(iterable,key=None,reverse=False)

返回一个排序的列表，使用方法和列表内置函数（list.sort()）一致。

>>> b
['b', 'e', 'i', 'j', 'i', 'n', 'g']
>>> sorted(b)
['b', 'e', 'g', 'i', 'i', 'j', 'n']
>>> c = 'beijing'
>>> sorted(c)
['b', 'e', 'g', 'i', 'i', 'j', 'n']
>>> 

-reversed(sequence)

返回逆向迭代序列的值，和列表内置函数（list.reverse()）一致。

>>> num
[1, 1, 2, 3, 5, 8]
>>> reversed(num)
<list_reverseiterator object at 0x022BFC50>
>>> list(reversed(num))
[8, 5, 3, 2, 1, 1]
>>> 

-enumerate(iterable)

生成由每个元素的index和item值组成的元组

>>> c
'beijing'
>>> enumerate(c)
<enumerate object at 0x022B2508>
>>> tuple(enumerate(c))
((0, 'b'), (1, 'e'), (2, 'i'), (3, 'j'), (4, 'i'), (5, 'n'), (6, 'g'))
>>> 
>>> list(enumerate(c))
[(0, 'b'), (1, 'e'), (2, 'i'), (3, 'j'), (4, 'i'), (5, 'n'), (6, 'g')]
>>> 

-zip(iter1 [,iter2 [...]])

返回由各个参数的序列组成的元组

>>> d = [1,2,4,5,6]
>>> e = [7,8,1,2]
>>> zip(d,e)
<zip object at 0x022A3788>
>>> list(zip(d,e))
[(1, 7), (2, 8), (4, 1), (5, 2)]
>>> tuple(zip(d,e))
((1, 7), (2, 8), (4, 1), (5, 2))
>>>