我的Python笔记02

声明：本文整理借鉴金角大王的Python之路,Day2 - Python基础2，仅供本人学习使用！！！

本节内容

1. 列表、元组操作
2. 字符串操作
3. 字典操作
4. 集合操作
5. 文件操作
6. 字符编码与转码

1. 列表、元组操作

列表是我们最以后最常用的数据类型之一，通过列表可以对数据实现最方便的存储、修改等操作

定义列表

1	names = ['Alex',"Tenglan",'Eric']

# 列表
name2 = ["shantianfang", "huojin", "jinyong", "eryuehe"]
print(name2)

# 循环显示元素
for i in name2:
    print(i)

通过下标访问列表中的元素，下标从0开始计数

1 2 3 4 5 6 7 8

>>> names[0] 'Alex' >>> names[2] 'Eric' >>> names[-1] 'Eric' >>> names[-2] #还可以倒着取 'Tenglan'

切片:取多个元素　　

# # 截取切片的使用，注意取值范围是左闭右开区间
# print(name2[1:3])
#
# # 从后向前取值,:前不能有负数
# print(name2[-1])
# print(name2[-3:-1])
#
# print(name2[:3])
# print(name2[0:3])

追加

# 追加
# name2.append("laoli")
# print(name2)

插入

# # 插入到huojin前
# name2.insert(1, "laozhang")
# print(name2)

修改

# # 修改掉huojin
# name2[2] = "zhangliao"
# print(name2)

删除

# 删除的方法一：
name2.remove("zhangliao")
# 删除的方法二：按列表的元素下标删除
# del name2[1]
# 删除列表：
# del name2

# 删除的方法三：默认从后往前删除最后一个
# name2.pop()
# 加入下标 name2.pop(1) 与 del name2[1] 同意
# name2.pop(1)
print(name2)

扩展

# 列表扩展
print(name2)
name3 = [1, 2, 3, 4]
name2.extend(name3)
print(name2,name3)

拷贝

 import copy  # 深Copy使用

name2 = ["4shantianfang", "#!huojin", "jinyong", "Eryuehe", "caocao"]# Copy列表

name4 = name2.copy()
print(name2)
print(name4)
# 修改列表，查看复制列表状态
name2[4] = "曹操"
print(name2)
print(name4)

====================================================================================================================================

name2 = ["4shantianfang", "#!huojin", ["tangseng", "wukong"], "jinyong", "Eryuehe", "caocao"]

# 深浅Copy列表
name4 = name2.copy()
print(name2)
print(name4)

# 修改列表中包含列表的元素,
name2[1] = "shaseng"
name2[2][1] = "zhubajie"
print(name2)
print(name4)

['4shantianfang', 'shaseng', ['tangseng', 'zhubajie'], 'jinyong', 'Eryuehe', 'caocao']
['4shantianfang', '#!huojin', ['tangseng', 'zhubajie'], 'jinyong', 'Eryuehe', 'caocao']

# 深浅Copy的原因和内存结构有关，这里的copy只是copy出列表中列表的内存地址，修改嵌套中的列表后直接按照地址找到斌修改

# 如果想完整的Copy出一份数据的如下操做
print("==" * 30)
name6 = copy.copy(name2)
print("name6:", name6)

# 深Copy
print("==" * 30)
name7 = copy.deepcopy(name2)  # 深Copy

print("name7:", name7)

============================================================
name6: ['4shantianfang', 'shaseng', ['tangseng', 'zhubajie'], 'jinyong', 'Eryuehe', 'caocao']
============================================================
name7: ['4shantianfang', 'shaseng', ['tangseng', 'zhubajie'], 'jinyong', 'Eryuehe', 'caocao']

copy真的这么简单么？那我还讲个屁。。。

# 清空列表
# print(name2.clear())
# print(name2)

统计

# # 统计元素
# print(name2.count("jinyong"))

排序&

name2 = ["4shantianfang", "#!huojin", "jinyong", "Eryuehe"]

# 排序命令
name2.sort()
print(name2)

翻转

# 反转命令
# name2.reverse()
# print(name2)

获取下标

 

元组

元组其实跟列表差不多，也是存一组数，只不是它一旦创建，便不能再修改，所以又叫只读列表

语法

1	names = ("alex","jack","eric")

它只有2个方法，一个是count,一个是index，完毕。　　

程序练习

请闭眼写出以下程序。

程序：购物车程序

需求:

1. 启动程序后，让用户输入工资，然后打印商品列表
2. 允许用户根据商品编号购买商品
3. 用户选择商品后，检测余额是否够，够就直接扣款，不够就提醒
4. 可随时退出，退出时，打印已购买商品和余额

2. 字符串操作　　　

特性：不可修改　

name.capitalize()  首字母大写
name.casefold()   大写全部变小写
name.center(50,"-")  输出 '---------------------Alex Li----------------------'
name.count('lex') 统计 lex出现次数
name.encode()  将字符串编码成bytes格式
name.endswith("Li")  判断字符串是否以 Li结尾
 "Alex\tLi".expandtabs(10) 输出'Alex      Li'， 将\t转换成多长的空格
 name.find('A')  查找A,找到返回其索引， 找不到返回-1 

format :
    >>> msg = "my name is {}, and age is {}"
    >>> msg.format("alex",22)
    'my name is alex, and age is 22'
    >>> msg = "my name is {1}, and age is {0}"
    >>> msg.format("alex",22)
    'my name is 22, and age is alex'
    >>> msg = "my name is {name}, and age is {age}"
    >>> msg.format(age=22,name="ale")
    'my name is ale, and age is 22'
format_map
    >>> msg.format_map({'name':'alex','age':22})
    'my name is alex, and age is 22'

msg.index('a')  返回a所在字符串的索引
'9aA'.isalnum()   True

'9'.isdigit() 是否整数
name.isnumeric
name.isprintable
name.isspace
name.istitle
name.isupper
 "|".join(['alex','jack','rain'])
'alex|jack|rain'

maketrans
    >>> intab = "aeiou"  #This is the string having actual characters.
    >>> outtab = "12345" #This is the string having corresponding mapping character
    >>> trantab = str.maketrans(intab, outtab)
    >>>
    >>> str = "this is string example....wow!!!"
    >>> str.translate(trantab)
    'th3s 3s str3ng 2x1mpl2....w4w!!!'

 msg.partition('is')   输出 ('my name ', 'is', ' {name}, and age is {age}') 

 >>> "alex li, chinese name is lijie".replace("li","LI",1)
     'alex LI, chinese name is lijie'

 msg.swapcase 大小写互换

 >>> msg.zfill(40)
'00000my name is {name}, and age is {age}'

>>> n4.ljust(40,"-")
'Hello 2orld-----------------------------'
>>> n4.rjust(40,"-")
'-----------------------------Hello 2orld'

>>> b="ddefdsdff_哈哈"
>>> b.isidentifier() #检测一段字符串可否被当作标志符，即是否符合变量命名规则
True

3. 字典操作

字典一种key - value 的数据类型，使用就像我们上学用的字典，通过笔划、字母来查对应页的详细内容。

语法:

# 字典操作：
# 特点：key-value的数据类型，唯一，无序的
info = {
    'stu1101': "Liang Xu",
    'stu1102': "YunRui Bai",
    'stu1103': "Ping Jiang",
}

字典的特性：

• dict是无序的
• key必须是唯一的,so 天生去重

增加

info["stu1104"] = "徐庆"
#不存在就创建

修改

# 存在的话就修改
info["stu1101"] = "徐良"

删除

# 删除功能:删除指定字符
# del info["stu1101"]
# info.pop("stu1104")

# 随机删除,我的是最后一个
# info.popitem()

查找

# 查找方法一：确定存在用下面，若存在返回，若不存在报错
# info["stu1104"]
# 查找方法二：存在就返回，不存在就是None
# print(info.get('stu1104'))
# 查找方法三：在就返回True，不在就返回False
# print('stu1101' in info)

多级字典嵌套及操作

xiaoshuo = {
    "shantianfang": {
        "baimeidaxia": ["xuliang", "baiyunrui"],
        "sanxiajian": ["shengying", "zhugeyuanying"],
        "suitangyanyi": ["qinqiong", "shanxiongxin"],
    },
    "jinyong": {
        "tianlongbabu": ["xiaofeng", "xuzhu", "duanyu"]
    },
    "eryuehe": {
        "1024": ["康熙王朝", "雍正王朝"]
    }
}

# 修改指定位置的字符
# xiaoshuo["eryuehe"]["1024"][1] = "乾隆王朝"
# 修改追加指定位置的字符
# xiaoshuo["eryuehe"]["1024"][1] += "，乾隆王朝"
# print(xiaoshuo["eryuehe"]["1024"])

print(xiaoshuo)

其它姿势

# 获取字典的值
# print(info.values())
#dict_values(['Liang Xu', 'YunRui Bai', 'Ping Jiang'])

# 获取字典的键
print(info.keys())
dict_keys(['stu1101', 'stu1102', 'stu1103'])

# 没有匹配的创建一个新的值，有的话就返回
# xiaoshuo.setdefault("huojin", {"34": ["shijianjianshi"]})
# xiaoshuo.setdefault("eryuehe", {"34": ["shijianjianshi"]})

# 字典更新，有则改之无则加之
info1 = {1: 2, 2: 3, "stu1105": "房书安", "stu1102": "笑天王白春"}
info.update(info1)
print(info)

{'stu1101': 'Liang Xu', 'stu1102': 'YunRui Bai', 'stu1103': 'Ping Jiang'}
{'stu1101': 'Liang Xu', 'stu1102': '笑天王白春', 'stu1103': 'Ping Jiang', 1: 2, 2: 3, 'stu1105': '房书安'}

# 把字典以列表形式遍历出来
print(info.items())

# 初始化一个新字典并附一个值
c = info.fromkeys([6, 7, 8], "test")
print(c)
print(info.items())

循环dict

#方法1比2较高效
for key in info:
    print(key,info[key])

#方法2
for k,v in info.items(): #会先把dict转成list,数据量大时候机器废了
    print(k,v)

程序练习

程序: 三级菜单

要求:

1. 打印省、市、县三级菜单
2. 可返回上一级
3. 可随时退出程序

 

4.集合操作

集合是一个无序的，不重复的数据组合，它的主要作用如下：

• 去重，把一个列表变成集合，就自动去重了
• 关系测试，测试两组数据之前的交集、差集、并集等关系

常用操作

# 集合的去重，将列表转换成集合
list_1 = [1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, 0]

# 将列表类型换行成集合类型
list_1 = set(list_1)

print(type(list_1), list_1)

# 交集方式一：

# list_3 = list_1.intersection(list_2)
# 交集方式二：
list_3 = list_1 & list_2
print(list_3)

# 对称差集方式一：
print(list_1.symmetric_difference(list_2))
# 对称差集方式二：
print(list_1 ^ list_2)

# Return True if two sets have a null intersection.
# 如果两个集合的交集为空，则返回True。
print(list_1.isdisjoint(list_2))

# 并集方式一：
# list_4 = list_1.union(list_2)
# 并集方式二：
list_4 = list_1 | list_2
print(list_4)

# 差集方式一：in list_1 but not in list_2 只在1里不在2里的
print(list_1.difference(list_2))
# print(list_2.difference(list_1))
# 差集方式二：
print(list_1 - list_2)

# 子集
list_6 = set([2, 3, 4])
print(list_6.issubset(list_2))

返回True

# 父集
print(list_6.issuperset(list_2))

返回False

# 集合的基本操作：
# 添加一项
# list_1.add(999)  
# print(list_1)

# 添加多项
list_1.update([100, 200, 300])
print(list_1)

# 删除动作：remove
# print(list_1.remove("eee"))

list_1.discard("1")
print(list_1.pop())
print(list_1)

5. 文件操作

对文件操作流程

1. 打开文件，得到文件句柄并赋值给一个变量
2. 通过句柄对文件进行操作
3. 关闭文件

现有文件如下

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
我曾千万次梦见
The splendid things I planned
那些我计划的绚丽蓝图
I always built to last on weak and shifting sand
但我总是将之建筑在易逝的流沙上
I lived by night and shunned the naked light of day
我夜夜笙歌 逃避白昼赤裸的阳光
And only now I see how the time ran away
事到如今我才看清岁月是如何匆匆流逝
Yesterday when I was young
昨日当我年少轻狂
So many lovely songs were waiting to be sung
有那么多甜美的曲儿等我歌唱
So many wild pleasures lay in store for me
有那么多肆意的快乐等我享受
And so much pain my eyes refused to see
还有那么多痛苦 我的双眼却视而不见
I ran so fast that time and youth at last ran out
我飞快地奔走 最终时光与青春消逝殆尽
I never stopped to think what life was all about
我从未停下脚步去思考生命的意义
And every conversation that I can now recall
如今回想起的所有对话
Concerned itself with me and nothing else at all
除了和我相关的 什么都记不得了
The game of love I played with arrogance and pride
我用自负和傲慢玩着爱情的游戏
And every flame I lit too quickly, quickly died
所有我点燃的火焰都熄灭得太快
The friends I made all somehow seemed to slip away
所有我交的朋友似乎都不知不觉地离开了
And only now I'm left alone to end the play, yeah
只剩我一个人在台上来结束这场闹剧
Oh, yesterday when I was young
噢 昨日当我年少轻狂
So many, many songs were waiting to be sung
有那么那么多甜美的曲儿等我歌唱
So many wild pleasures lay in store for me
有那么多肆意的快乐等我享受
And so much pain my eyes refused to see
还有那么多痛苦 我的双眼却视而不见
There are so many songs in me that won't be sung
我有太多歌曲永远不会被唱起
I feel the bitter taste of tears upon my tongue
我尝到了舌尖泪水的苦涩滋味
The time has come for me to pay for yesterday
终于到了付出代价的时间 为了昨日
When I was young
当我年少轻狂

 

"""编码：UTF-8和GBK的区别？
UnicodeDecodeError: 'gbk' codec can't decode byte 0x80 in position 106: illegal multibyte sequence
为避免上述错误加入, encoding="UTF-8"
"""

data = open("yesterday.txt", encoding="UTF-8").read()
print(data)

基本操作　　

1 2 3 4 5 6 7 8

f = open('lyrics') #打开文件 first_line = f.readline() print('first line:',first_line) #读一行 print('我是分隔线'.center(50,'-')) data = f.read()# 读取剩下的所有内容,文件大时不要用 print(data) #打印文件   f.close() #关闭文件

打开文件的模式有：

• r，只读模式（默认）。
• w，只写模式。【不可读；不存在则创建；存在则删除内容；】
• a，追加模式。【可读；   不存在则创建；存在则只追加内容；】

"+" 表示可以同时读写某个文件

• r+，可读写文件。【可读；可写；可追加】
• w+，写读
• a+，同a

"U"表示在读取时，可以将 \r \n \r\n自动转换成 \n （与 r 或 r+ 模式同使用）

• rU
• r+U

"b"表示处理二进制文件（如：FTP发送上传ISO镜像文件，linux可忽略，windows处理二进制文件时需标注）

• rb
• wb
• ab

其它语法

    def close(self): # real signature unknown; restored from __doc__
        """
        Close the file.

        A closed file cannot be used for further I/O operations.  close() may be
        called more than once without error.
        """
        pass

    def fileno(self, *args, **kwargs): # real signature unknown
        """ Return the underlying file descriptor (an integer). """
        pass

    def isatty(self, *args, **kwargs): # real signature unknown
        """ True if the file is connected to a TTY device. """
        pass

    def read(self, size=-1): # known case of _io.FileIO.read
        """
        注意，不一定能全读回来
        Read at most size bytes, returned as bytes.

        Only makes one system call, so less data may be returned than requested.
        In non-blocking mode, returns None if no data is available.
        Return an empty bytes object at EOF.
        """
        return ""

    def readable(self, *args, **kwargs): # real signature unknown
        """ True if file was opened in a read mode. """
        pass

    def readall(self, *args, **kwargs): # real signature unknown
        """
        Read all data from the file, returned as bytes.

        In non-blocking mode, returns as much as is immediately available,
        or None if no data is available.  Return an empty bytes object at EOF.
        """
        pass

    def readinto(self): # real signature unknown; restored from __doc__
        """ Same as RawIOBase.readinto(). """
        pass #不要用,没人知道它是干嘛用的

    def seek(self, *args, **kwargs): # real signature unknown
        """
        Move to new file position and return the file position.

        Argument offset is a byte count.  Optional argument whence defaults to
        SEEK_SET or 0 (offset from start of file, offset should be >= 0); other values
        are SEEK_CUR or 1 (move relative to current position, positive or negative),
        and SEEK_END or 2 (move relative to end of file, usually negative, although
        many platforms allow seeking beyond the end of a file).

        Note that not all file objects are seekable.
        """
        pass

    def seekable(self, *args, **kwargs): # real signature unknown
        """ True if file supports random-access. """
        pass

    def tell(self, *args, **kwargs): # real signature unknown
        """
        Current file position.

        Can raise OSError for non seekable files.
        """
        pass

    def truncate(self, *args, **kwargs): # real signature unknown
        """
        Truncate the file to at most size bytes and return the truncated size.

        Size defaults to the current file position, as returned by tell().
        The current file position is changed to the value of size.
        """
        pass

    def writable(self, *args, **kwargs): # real signature unknown
        """ True if file was opened in a write mode. """
        pass

    def write(self, *args, **kwargs): # real signature unknown
        """
        Write bytes b to file, return number written.

        Only makes one system call, so not all of the data may be written.
        The number of bytes actually written is returned.  In non-blocking mode,
        returns None if the write would block.
        """
        pass

with语句

为了避免打开文件后忘记关闭，可以通过管理上下文，即：

1 2 3

with open('log','r') as f:           ...

如此方式，当with代码块执行完毕时，内部会自动关闭并释放文件资源。

在Python 2.7 后，with又支持同时对多个文件的上下文进行管理，即：

1 2	with open('log1') as obj1, open('log2') as obj2:     pass

程序练习　　

程序1: 实现简单的shell sed替换功能

程序2:修改haproxy配置文件 

需求：

1、查
    输入：www.oldboy.org
    获取当前backend下的所有记录

2、新建
    输入：
        arg = {
            'bakend': 'www.oldboy.org',
            'record':{
                'server': '100.1.7.9',
                'weight': 20,
                'maxconn': 30
            }
        }

3、删除
    输入：
        arg = {
            'bakend': 'www.oldboy.org',
            'record':{
                'server': '100.1.7.9',
                'weight': 20,
                'maxconn': 30
            }
        }

原配置文件
global
        log 127.0.0.1 local2
        daemon
        maxconn 256
        log 127.0.0.1 local2 info
defaults
        log global
        mode http
        timeout connect 5000ms
        timeout client 50000ms
        timeout server 50000ms
        option  dontlognull

listen stats :8888
        stats enable
        stats uri       /admin
        stats auth      admin:1234

frontend oldboy.org
        bind 0.0.0.0:80
        option httplog
        option httpclose
        option  forwardfor
        log global
        acl www hdr_reg(host) -i www.oldboy.org
        use_backend www.oldboy.org if www

backend www.oldboy.org
        server 100.1.7.9 100.1.7.9 weight 20 maxconn 3000

6. 字符编码与转码

详细文章:

http://www.cnblogs.com/yuanchenqi/articles/5956943.html

http://www.diveintopython3.net/strings.html

需知:

1.在python2默认编码是ASCII, python3里默认是unicode

2.unicode 分为 utf-32(占4个字节),utf-16(占两个字节)，utf-8(占1-4个字节)， so utf-16就是现在最常用的unicode版本， 不过在文件里存的还是utf-8，因为utf8省空间

3.在py3中encode,在转码的同时还会把string 变成bytes类型，decode在解码的同时还会把bytes变回string

上图仅适用于py2

#-*-coding:utf-8-*-
__author__ = 'Alex Li'

import sys
print(sys.getdefaultencoding())

msg = "我爱北京天安门"
msg_gb2312 = msg.decode("utf-8").encode("gb2312")
gb2312_to_gbk = msg_gb2312.decode("gbk").encode("gbk")

print(msg)
print(msg_gb2312)
print(gb2312_to_gbk)

in python2

#-*-coding:gb2312 -*-   #这个也可以去掉
__author__ = 'Alex Li'

import sys
print(sys.getdefaultencoding())

msg = "我爱北京天安门"
#msg_gb2312 = msg.decode("utf-8").encode("gb2312")
msg_gb2312 = msg.encode("gb2312") #默认就是unicode,不用再decode,喜大普奔
gb2312_to_unicode = msg_gb2312.decode("gb2312")
gb2312_to_utf8 = msg_gb2312.decode("gb2312").encode("utf-8")

print(msg)
print(msg_gb2312)
print(gb2312_to_unicode)
print(gb2312_to_utf8)

in python3

7.  内置函数

未完待续。。。