Python 序列容器

浏览数：20 / 时间：2015年06月08日

Python中sequence主要包含存储单个元素序列和两个元素对的序列，str就是一个字符容器。

单元素序列主要有以下类型：

bytearray: 字节数组，通过built-in 函数bytearray()创建

xrange：由函数xrange(n)/xrange(start, stop, step)创建，但不支持容器上的切片，连接，复制， in/not in 判断，min/max取值操作， xrange是

immutable sequence, xrange对象大小固定，与其代表范围大小无关，xrange主要用于循环，比range效率稍高，xrange上的操作只支持indexing, iteration, len

list：链表mutable, [a,b,c]，相当于其他语言中的数组链表集合体，因此也就部分LinkList和ArrayList

tuple: immutable list，非空tuple括号可有可无a,b,c 或(a,b,c) , empty tuple必须有括号(), single item tuple 逗号必不可少 a, 或(a,);不能对tuple的某个元素赋值，但tuple中的元素可以是mutable

set: mutable unordered hashtable, 支持数学操作并集合集等，因为无序，所以不支持indexing，slicing等顺序性操作飞空{a,b,c} 空set()，支持issubset/union/intersection/difference

frozenset: immutable unordered hashtable

双元素序列则主要是关联数组：

dict: hash_table, comma-separated list of key-value: {a:b, c:d} , empty dic: dic()，主要有以下方法：

iter(d) is short for iterkeys()

get(key)/has_key(key)/pop(key)/popitem()

items(): return a copy of the dictionary‘s list of (key, value) pairs

keys(): return a list of keys

sorted(keys()): return a sorted list of keys

dictview: dict.viewkeys()/viewvalues()/viewitems() 返回，是dict的view，即dict变了，view也会变

Sequence主要操作就是增删改查，以下查操作优先级依次递增，s、t类型相同，n、i、j 是整形

Operation	Result	Notes
`x in s`	`True` if an item of s is equal to x, else `False`	(1)
`x not in s`	`False` if an item of s is equal to x, else `True`	(1)
`s + t`	the concatenation of s and t	(6)
`s * n, n * s`	n shallow copies of s concatenated	(2)
`s[i]`	ith item of s, origin 0	(3)
`s[i:j]`	slice of s from i to j	(3)(4)
`s[i:j:k]`	slice of s from i to j with step k	(3)(5)
`len(s)`	length of s
`min(s)`	smallest item of s
`max(s)`	largest item of s
`s.index(x)`	index of the first occurrence of x in s
`s.count(x)`	total number of occurrences of x in s

容器之间也可以进行比较，依次比较容器中的每一个元素

如果s是str/unicode, in/not in 判断x是否是s的字串

n<0时s*n = s*0 返回类型与s相同的空容器

如果i/j < 0, s[i/j] 的位置为len(s) + i/j, 但s[0]=s[-0]

i,j都可以省略，省略i则i=0, 省略j 则j=len(s), 如果i/j>len(s), 则取len(s), 如果i>=j, 则slice返回空

Sequence按可变性又可分为mutable和immutable：

immutable sequence: string, xrange, tuple, 一旦创建，不能再改变

mutable sequence: bytearray, list 可以添加元素或改变某个位置的元素，可变容器支持以下操作

Operation	Result	Notes
`s[i] = x`	item i of s is replaced by x
`s[i:j] = t`	slice of s from i to j is replaced by the contents of the iterable t
`del s[i:j]`	same as `s[i:j] = []`
`s[i:j:k] = t`	the elements of `s[i:j:k]` are replaced by those of t	(1)
`del s[i:j:k]`	removes the elements of `s[i:j:k]` from the list
`s.append(x)`	same as `s[len(s):len(s)] = [x]`	(2)
`s.extend(x)`	same as `s[len(s):len(s)] = x`	(3)
`s.count(x)`	return number of i‘s for which `s[i] == x`
`s.index(x[, i[, j]])`	return smallest k such that `s[k] == x` and `i <= k < j`	(4)
`s.insert(i, x)`	same as `s[i:i] = [x]`	(5)
`s.pop([i])`	same as `x = s[i]; del s[i]; return x`	(6)
`s.remove(x)`	same as `del s[s.index(x)]`	(4)
`s.reverse()`	reverses the items of s in place	(7)
`s.sort([cmp[, key[, reverse]]])`	sort the items of s in place	(7)(8)(9)(10)