标签：
1.集合操作
2.文件操作
3.字符编码与转码
4.函数操作
1.集合操作
集合是一个无序的、不重复的数据组合；
它的作用是：
1）自动去重：列表变成集合，自动去重；
>>> list_1 = [1,4,4,5,6,7,9,10]
>>> list_1 =set(list_1)
>>> print(list_1)
{1, 4, 5, 6, 7, 9, 10}
2）关系测试：测试两组数据之间的关系，交集、并集、差集、对称差集、父集、子集等
#交集 intersection &
>>> list_1 = set([1,4,4,5,6,7,9,10])
>>> list_2 = set([2,45,6,11])
>>> print(list_1.intersection(list_2)) #list_1和list_2的交集
{6}
>>> print(list_1 & list_2)
{6}
#并集 union |
>>> list_1 = set([1,4,4,5,6,7,9,10])
>>> list_2 = set([2,45,6,11])
>>> print(list_1.union(list_2))
{1, 2, 4, 5, 6, 7, 9, 10, 11, 45}
>>> print(list_1 | list_2)
{1, 2, 4, 5, 6, 7, 9, 10, 11, 45}
#差集 in list_1 but not in list_2 ----difference
>>> list_1 = set([1,4,4,5,6,7,9,10])
>>> list_2 = set([2,45,6,11])
>>> print(list_1.difference(list_2))
{1, 4, 5, 7, 9, 10}
>>> print(list_1 - list_2)
{1, 4, 5, 7, 9, 10}
#对称差集 symmetric_difference ----去掉两者相同的数据后合并
>>> list_1 = set([1,4,4,5,6,7,9,10])
>>> list_2 = set([2,45,6,11])
>>> print(list_1.symmetric_difference(list_2))
{1, 2, 4, 5, 7, 9, 10, 11, 45}
>>> print(list_1 ^ list_2)
{1, 2, 4, 5, 7, 9, 10, 11, 45}
#子集 issubset
>>> list_1 = set([1,2,3,4,5,6])
>>> list_2 = set([1,4])
>>> print(list_1.issubset(list_2))
False
>>> print(list_2.issubset(list_1))
True
#父集 issuperset
>>> list_1 = set([1,2,3,4,5,6])
>>> list_2 = set([1,4])
>>> print(list_1.issuperset(list_2))
True
>>> print(list_2.issuperset(list_1))
False
#没有交集则为true,有交集为false
>>> list_1 = set([1,2,3,4,5,6])
>>> list_2 = set([1,4])
>>> print(list_1.isdisjoint(list_2))
false
#添加一项
>>> list1 = set([1,3,4,6,7])
>>> list1.add(10)
>>> print(list1)
{1, 3, 4, 6, 7, 10}
#添加多项
>>> list1 = set([1,2])
>>> list1.update([6,8,10])
{8, 1, 2, 10, 6}
#remove ---删除不存在的元素会报错
>>> list1 = set([1,2,6,8,10])
>>> list1.remove(2)
>>> print(list1)
{8, 1, 10, 6}
>>> list1.remove(11)
>>> print(list1)
Traceback (most recent call last):
File "C:/Users/Administrator/PycharmProjects/cc/day3/set_test.py", line 2, in <module>
list1.remove(11)
KeyError: 11
#discard ---remove的友好版本，删除不存在的元素不会报错
>>> list1 = set([1,2,6,8,10])
>>> list1.discard(2)
>>> print(list1)
{8, 1, 10, 6}
>>> list1.discard(11)
>>> print(list1)
{8, 1, 2, 10, 6}
#pop ---随机删除
>>> list1 = set([1,2,6,8,10])
>>> list1.pop()
>>> print(list1)
{1, 2, 10, 6} ---因集合是无序的，故随机删除某一项
对文件操作流程：
2.1 打开文件
#文件句柄 = open(‘文件路径‘, ‘模式‘)
文件名：yesterday
Somehow, it seems the love I knew was always the most destructive kind 不知为何，我经历的爱情总是最具毁灭性的的那种 Yesterday when I was young 昨日当我年少轻狂 The taste of life was sweet 生命的滋味是甜的 As rain upon my tongue 就如舌尖上的雨露 I teased at life as if it were a foolish game 我戏弄生命 视其为愚蠢的游戏 The way the evening breeze 就如夜晚的微风 May tease the candle flame 逗弄蜡烛的火苗 The thousand dreams I dreamed
打开文件的模式有：
>>> f = open("yesterday,‘r‘,encoding="utf-8")
>>> a = f.read()
>>> print(a)
>>> f.close()
Somehow, it seems the love I knew was always the most destructive kind
不知为何，我经历的爱情总是最具毁灭性的的那种
Yesterday when I was young
昨日当我年少轻狂
The taste of life was sweet
生命的滋味是甜的
As rain upon my tongue
就如舌尖上的雨露
I teased at life as if it were a foolish game
我戏弄生命 视其为愚蠢的游戏
The way the evening breeze
就如夜晚的微风
May tease the candle flame
逗弄蜡烛的火苗
The thousand dreams I dreamed
>>> f = open("1.txt",‘w‘,encoding="utf-8")
>>> f = open("1.txt",‘a‘,encoding="utf-8")
"+" 表示可以同时读写某个文件
>>> f = open("1.txt",‘r+‘,encoding="utf-8")
>>> f = open("1.txt",‘w+‘,encoding="utf-8")
>>> f = open("1.txt",‘a+‘,encoding="utf-8")
"b"表示以字节的方式操作
注：以b方式打开时，读取到的内容是字节类型，写入时也需要提供字节类型
2.2 操作文件
read()
read() 每次读取整个文件，它通常用于将文件内容放到一个字符串变量中。然而 read() 生成文件内容最直接的字符串表示，但对于连续的面向行的处理，它却是不必要的，并且如果文件大于可用内存，则不可能实现这种处理。
>>> f = open("yesterday,‘r‘,encoding="utf-8")
>>> a = f.read()
>>> print(a)
>>> f.close()
Somehow, it seems the love I knew was always the most destructive kind
不知为何，我经历的爱情总是最具毁灭性的的那种
Yesterday when I was young
昨日当我年少轻狂
The taste of life was sweet
生命的滋味是甜的
As rain upon my tongue
就如舌尖上的雨露
I teased at life as if it were a foolish game
我戏弄生命 视其为愚蠢的游戏
The way the evening breeze
就如夜晚的微风
May tease the candle flame
逗弄蜡烛的火苗
The thousand dreams I dreamed
readlines()---适合读小文件
一次读取整个文件，象 read() 一样，readlines() 自动将文件内容分析成一个行的列表，该列表可以由 Python 的 for ... in ... 结构进行处理。
>>> f = open("yesterday","r",encoding="utf-8")#文件句柄
>>> for index,line in enumerate(f.readlines()):
>>> if index == 9:
>>> print(‘---我是分割线---‘)
>>> continue
>>> print(line.strip())
>>> f.close()
Somehow, it seems the love I knew was always the most destructive kind
不知为何，我经历的爱情总是最具毁灭性的的那种
Yesterday when I was young
昨日当我年少轻狂
The taste of life was sweet
生命的滋味是甜的
As rain upon my tongue
就如舌尖上的雨露
I teased at life as if it were a foolish game
---我是分割线---
The way the evening breeze
就如夜晚的微风
May tease the candle flame
逗弄蜡烛的火苗
The thousand dreams I dreamed
readline() 每次只读取一行
>>> f = open("yesterday","r",encoding="utf-8")#文件句柄
>>> a = f.readline()
>>> print(a)
>>> f.close()
Somehow, it seems the love I knew was always the most destructive kind
>>> f = open("yesterday","r",encoding="utf-8")#文件句柄
>>> for line in f:
>>> print(line.strip())
>>> f.close()
Somehow, it seems the love I knew was always the most destructive kind
不知为何，我经历的爱情总是最具毁灭性的的那种
Yesterday when I was young
昨日当我年少轻狂
The taste of life was sweet
生命的滋味是甜的
As rain upon my tongue
就如舌尖上的雨露
I teased at life as if it were a foolish game
我戏弄生命 视其为愚蠢的游戏
The way the evening breeze
就如夜晚的微风
May tease the candle flame
逗弄蜡烛的火苗
The thousand dreams I dreamed
2.3 管理上下文--with语句
上面我们可以看到，每次打开后都需要关闭文件，十分繁琐。。。
为了避免打开文件后忘记关闭，可以通过管理上下文，即：
>>> with open("yesterday","r",encoding="utf-8") as f:
>>> .....
#告知当前光标的位置 >>> f = open(‘yesterday‘,‘r‘,encoding=‘utf-8‘) >>> print(f.tell()) 0 #光标回到首位 >>> f.seek(0) #判断是否可移动 >>> f.seekable #判断文件是否可读 >>> f.readable() #判断文件是否可写 >>> f.writable() #文件描述符 f.flieno()
python学习笔记-（七）python基础--集合、文件操作&函数
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原文地址：http://www.cnblogs.com/cocc/p/5746311.html
