python3 基础 笔记记录-2

Posted 2020-10-05

http://www.cnblogs.com/alex3714/articles/5717620.html
列表、元组操作
字符串操作
字典操作
集合操作
文件操作
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
        names = [‘Alex‘,"Tenglan",‘Eric‘]
    通过下标访问列表中的元素，下标从0开始计数
        >>> 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
        >>> names = ["Alex","Tenglan","Eric","Rain","Tom","Amy"]
        >>> names[1:4]  #取下标1至下标4之间的数字，包括1，不包括4
        [‘Tenglan‘, ‘Eric‘, ‘Rain‘]
        >>> names[1:-1] #取下标1至-1的值，不包括-1
        [‘Tenglan‘, ‘Eric‘, ‘Rain‘, ‘Tom‘]
        >>> names[0:3]
        [‘Alex‘, ‘Tenglan‘, ‘Eric‘]
        >>> names[:3] #如果是从头开始取，0可以忽略，跟上句效果一样
        [‘Alex‘, ‘Tenglan‘, ‘Eric‘]
        >>> names[3:] #如果想取最后一个，必须不能写-1，只能这么写
        [‘Rain‘, ‘Tom‘, ‘Amy‘]
        >>> names[3:-1] #这样-1就不会被包含了
        [‘Rain‘, ‘Tom‘]
        >>> names[0::2] #后面的2是代表，每隔一个元素，就取一个
        [‘Alex‘, ‘Eric‘, ‘Tom‘]
        >>> names[::2] #和上句效果一样
        [‘Alex‘, ‘Eric‘, ‘Tom‘]

    追加
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Eric‘, ‘Rain‘, ‘Tom‘, ‘Amy‘]
        >>> names.append("我是新来的")
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Eric‘, ‘Rain‘, ‘Tom‘, ‘Amy‘, ‘我是新来的‘]
    插入
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Eric‘, ‘Rain‘, ‘Tom‘, ‘Amy‘, ‘我是新来的‘]
        >>> names.insert(2,"强行从Eric前面插入")
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘强行从Eric前面插入‘, ‘Eric‘, ‘Rain‘, ‘Tom‘, ‘Amy‘, ‘我是新来的‘]

        >>> names.insert(5,"从eric后面插入试试新姿势")
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘强行从Eric前面插入‘, ‘Eric‘, ‘Rain‘, ‘从eric后面插入试试新姿势‘, ‘Tom‘, ‘Amy‘, ‘我是新来的‘]
    修改
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘强行从Eric前面插入‘, ‘Eric‘, ‘Rain‘, ‘从eric后面插入试试新姿势‘, ‘Tom‘, ‘Amy‘, ‘我是新来的‘]
        >>> names[2] = "该换人了"
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘该换人了‘, ‘Eric‘, ‘Rain‘, ‘从eric后面插入试试新姿势‘, ‘Tom‘, ‘Amy‘, ‘我是新来的‘]
    删除
        >>> del names[2]
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Eric‘, ‘Rain‘, ‘从eric后面插入试试新姿势‘, ‘Tom‘, ‘Amy‘, ‘我是新来的‘]
        >>> del names[4]
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Eric‘, ‘Rain‘, ‘Tom‘, ‘Amy‘, ‘我是新来的‘]
        >>>
        >>> names.remove("Eric") #删除指定元素
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Rain‘, ‘Tom‘, ‘Amy‘, ‘我是新来的‘]
        >>> names.pop() #删除列表最后一个值
        ‘我是新来的‘
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Rain‘, ‘Tom‘, ‘Amy‘]
    扩展
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Rain‘, ‘Tom‘, ‘Amy‘]
        >>> b = [1,2,3]
        >>> names.extend(b)
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Rain‘, ‘Tom‘, ‘Amy‘, 1, 2, 3]
    拷贝
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Rain‘, ‘Tom‘, ‘Amy‘, 1, 2, 3]

        >>> name_copy = names.copy()
        >>> name_copy
        [‘Alex‘, ‘Tenglan‘, ‘Rain‘, ‘Tom‘, ‘Amy‘, 1, 2, 3]
    统计
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Amy‘, ‘Tom‘, ‘Amy‘, 1, 2, 3]
        >>> names.count("Amy")
        2
    排序&翻转
        >>> names
        [‘Alex‘, ‘Tenglan‘, ‘Amy‘, ‘Tom‘, ‘Amy‘, 1, 2, 3]
        >>> names.sort() #排序
        Traceback (most recent call last):
          File "<stdin>", line 1, in <module>
        TypeError: unorderable types: int() < str()   #3.0里不同数据类型不能放在一起排序了，擦
        >>> names[-3] = ‘1‘
        >>> names[-2] = ‘2‘
        >>> names[-1] = ‘3‘
        >>> names
        [‘Alex‘, ‘Amy‘, ‘Amy‘, ‘Tenglan‘, ‘Tom‘, ‘1‘, ‘2‘, ‘3‘]
        >>> names.sort()
        >>> names
        [‘1‘, ‘2‘, ‘3‘, ‘Alex‘, ‘Amy‘, ‘Amy‘, ‘Tenglan‘, ‘Tom‘]

        >>> names.reverse() #反转
        >>> names
        [‘Tom‘, ‘Tenglan‘, ‘Amy‘, ‘Amy‘, ‘Alex‘, ‘3‘, ‘2‘, ‘1‘]
    获取下标
        >>> names
        [‘Tom‘, ‘Tenglan‘, ‘Amy‘, ‘Amy‘, ‘Alex‘, ‘3‘, ‘2‘, ‘1‘]
        >>> names.index("Amy")
        2 #只返回找到的第一个下标

2.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  names = ("alex","jack","eric")

        它只有2个方法，一个是count,一个是index，完毕。

3.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

4.字典
    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:
        info = {
            ‘stu1101‘: "TengLan Wu",
            ‘stu1102‘: "LongZe Luola",
            ‘stu1103‘: "XiaoZe Maliya",
        }
    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"] = "苍井空"
        >>> info
        {‘stu1102‘: ‘LongZe Luola‘, ‘stu1104‘: ‘苍井空‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1101‘: ‘TengLan Wu‘}
    修改
        >>> info[‘stu1101‘] = "武藤兰"
        >>> info
        {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1101‘: ‘武藤兰‘}
    删除
        >>> info
        {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1101‘: ‘武藤兰‘}
        >>> info.pop("stu1101") #标准删除姿势
        ‘武藤兰‘
        >>> info
        {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘}
        >>> del info[‘stu1103‘] #换个姿势删除
        >>> info
        {‘stu1102‘: ‘LongZe Luola‘}
        >>>
        >>>
        >>>
        >>> info = {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘}
        >>> info
        {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘} #随机删除
        >>> info.popitem()
        (‘stu1102‘, ‘LongZe Luola‘)
        >>> info
        {‘stu1103‘: ‘XiaoZe Maliya‘}
    查找
        >>> info = {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘}
        >>>
        >>> "stu1102" in info #标准用法
        True
        >>> info.get("stu1102")  #获取
        ‘LongZe Luola‘
        >>> info["stu1102"] #同上，但是看下面
        ‘LongZe Luola‘
        >>> info["stu1105"]  #如果一个key不存在，就报错，get不会，不存在只返回None
        Traceback (most recent call last):
          File "<stdin>", line 1, in <module>
        KeyError: ‘stu1105‘
    多字典的嵌套操作
        av_catalog = {
            "欧美":{
                "www.youporn.com": ["很多免费的,世界最大的","质量一般"],
                "www.pornhub.com": ["很多免费的,也很大","质量比yourporn高点"],
                "letmedothistoyou.com": ["多是自拍,高质量图片很多","资源不多,更新慢"],
                "x-art.com":["质量很高,真的很高","全部收费,屌比请绕过"]
            },
            "日韩":{
                "tokyo-hot":["质量怎样不清楚,个人已经不喜欢日韩范了","听说是收费的"]
            },
            "大陆":{
                "1024":["全部免费,真好,好人一生平安","服务器在国外,慢"]
            }
        }

        av_catalog["大陆"]["1024"][1] += ",可以用爬虫爬下来"
        print(av_catalog["大陆"]["1024"])
        #ouput
        [‘全部免费,真好,好人一生平安‘, ‘服务器在国外,慢,可以用爬虫爬下来‘]

    其他姿势
        #values
        >>> info.values()
        dict_values([‘LongZe Luola‘, ‘XiaoZe Maliya‘])

        #keys
        >>> info.keys()
        dict_keys([‘stu1102‘, ‘stu1103‘])


        #setdefault
        >>> info.setdefault("stu1106","Alex")
        ‘Alex‘
        >>> info
        {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1106‘: ‘Alex‘}
        >>> info.setdefault("stu1102","龙泽萝拉")
        ‘LongZe Luola‘
        >>> info
        {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1106‘: ‘Alex‘}


        #update
        >>> info
        {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1106‘: ‘Alex‘}
        >>> b = {1:2,3:4, "stu1102":"龙泽萝拉"}
        >>> info.update(b)
        >>> info
        {‘stu1102‘: ‘龙泽萝拉‘, 1: 2, 3: 4, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1106‘: ‘Alex‘}

        #items
        info.items()
        dict_items([(‘stu1102‘, ‘龙泽萝拉‘), (1, 2), (3, 4), (‘stu1103‘, ‘XiaoZe Maliya‘), (‘stu1106‘, ‘Alex‘)])


        #通过一个列表生成默认dict,有个没办法解释的坑，少用吧这个
        >>> dict.fromkeys([1,2,3],‘testd‘)
        {1: ‘testd‘, 2: ‘testd‘, 3: ‘testd‘}

    循环dict
        #方法1
        for key in info:
            print(key,info[key])

        #方法2
        for k,v in info.items(): #会先把dict转成list,数据里大时莫用
            print(k,v)