Python3基础——序列类型

开头写给自己，To Myself：

很久以来，都想要学习一门编程语言，从去年选择了python开始，反反复复重新开始了N多遍，每一次不会超过俩星期。昨天无意间翻开自己去年记的学习笔记，不禁感叹想当年我曾那么用功，却未能坚持下来，着实可惜。这一次，我告诉自己，最后一次机会，必须坚持到底！must。。。。。。

Sequence Types — list, tuple, range

Common Sequence Operations

Operation	Result	Notes
x in s	True if an item of s is equal to x, else False——关系操作符	(1)
x not in s	False if an item of s is equal to x, else True——关系操作符	(1)
s + t	the concatenation of s and t——连接操作符	(6)(7)
s * n or n * s	equivalent to adding s to itself n times——重复操作符	(2)(7)
s[i]	ith item of s, origin 0——获取下标位i的元素，下标从0开始	(3)
s[i:j]	slice of s from i to j——切片拷贝	(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[, i[, j]])	index of the first occurrence of x in s (at or after index i and before index j) 元素x在s中最早出现的位置下标，可以设置下标所在范围的起始位置	(8)
s.count(x)	total number of occurrences of x in s——元素x在序列s中出现的次数

Immutable Sequence Types

hash()

Mutable Sequence Types

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)	appends x to the end of the sequence (same as s[len(s):len(s)] = [x])
s.clear()	removes all items from s (same as del s[:])	(5)
s.copy()	creates a shallow copy of s (same as s[:])	(5)
s.extend(t) or s += t	extends s with the contents of t (for the most part the same as s[len(s):len(s)] = t)
s *= n	updates s with its contents repeated n times	(6)
s.insert(i, x)	inserts x into s at the index given by i (same as s[i:i] = [x])
s.pop([i])	retrieves the item at i and also removes it from s	(2)
s.remove(x)	remove the first item from s where s[i] == x	(3)
s.reverse()	reverses the items of s in place	(4)

Lists

1、创建列表的方法：

• Using a pair of square brackets to denote the empty list: []
• Using square brackets, separating items with commas: [a], [a, b, c]
• Using a list comprehension: [x for x in iterable]
• Using the type constructor: list() or list(iterable)

　　　　list('abc') returns ['a', 'b', 'c']

　　　　list( (1, 2, 3) ) returns [1, 2, 3]

2、除了以上方法外，列表还支持sort()方法

　　sort(*, key=None, reverse=None)

对列表进行排序，默认是按照从小到大的顺序排列

Tuples

1、创建元组的方法：

• Using a pair of parentheses to denote the empty tuple: ()
• Using a trailing comma for a singleton tuple: a, or (a,)
• Separating items with commas: a, b, c or (a, b, c)
• Using the tuple() built-in: tuple() or tuple(iterable)

       For example, tuple('abc') returns ('a', 'b', 'c') and tuple( [1, 2, 3] ) returns (1, 2, 3). 

注意：当你要创建的元组只有一个元素时，必须带逗号

Ranges

代表一组不可变的数字序列，主要用于for循环

class range(stop)

class range(start, stop[, step])

参数必须为整数，step步幅默认为1，start开始参数默认为0、

>>> list(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> list(range(1, 11))
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> list(range(0, 30, 5))
[0, 5, 10, 15, 20, 25]
>>> list(range(0, 10, 3))
[0, 3, 6, 9]
>>> list(range(0, -10, -1))
[0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
>>> list(range(0))
[]
>>> list(range(1, 0))
[]

列表、元组、字符串总结
共同点：
都可以通过索引得到每一个元素
默认索引值从0开始
可以用通过分片得到一个范围内的元素的集合
有很多共同的操作符（重复、拼接、成员关系操作符）