Summary：learn python 2

list

list切片[]

倒序输出list[::-1]

[a:b:c]
a start

b stop but not include this value

c interval

list.append() 尾部加入元素

list.insert(2,'string')   下标2的位置插入字符串string

>>> 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

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扩展

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拷贝

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copy真的这么简单么？那我还讲个屁。。。

统计

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排序&翻转

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获取下标

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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

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names = ("alex","jack","eric")

它只有2个方法，一个是count,一个是index，完毕。

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.isprintablename.isspacename.istitlename.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:

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

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修改

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删除

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查找

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多级字典嵌套及操作

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其它姿势

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循环dict 

#方法1for key in info:    print(key,info[key])#方法2for k,v in info.items(): #会先把dict转成list,数据里大时莫用    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

 

 三年菜单文艺青年版

 

 

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

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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 

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基本操作　　

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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：

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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：

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

    pass

data from 金角大王

tuple

dict

string

set