本節內容

1. 列表、元組操作
2. 字串操作
3. 字典操作
4. 集合操作
5. 檔案操作
6. 字元編碼與轉碼

1. 列表、元組操作

列表是我們最以後最常用的資料型別之一，通過列表可以對資料實現最方便的儲存、修改等操作

定義列表

通過下標訪問列表中的元素，下標從0開始計數

切片:取多個元素　　

追加

插入

修改

刪除

擴充套件

拷貝

copy真的這麼簡單麼？那我還講個屁。。。

統計

排序&翻轉

獲取下標

元組

元組其實跟列表差不多，也是存一組數，只不是它一旦建立，便不能再修改，所以又叫只讀列表

語法

它只有2個方法，一個是count,一個是index，完畢。　　

程式練習

請閉眼寫出以下程式。

程式：購物車程式

需求:

1. 啟動程式後，讓使用者輸入工資，然後列印商品列表
2. 允許使用者根據商品編號購買商品
3. 使用者選擇商品後，檢測餘額是否夠，夠就直接扣款，不夠就提醒
4. 可隨時退出，退出時，列印已購買商品和餘額

2. 字串操作　　　

特性：不可修改　

name.capitalize()  首字母大寫
name.casefold()   大寫全部變小寫
name.center(50,"-")  輸出 '---------------------Alex Li----------------------'
name.count('lex') 統計 lex出現次數
name.encode()  將字串編碼成bytes格式
name.endswith("Li")  判斷字串是否以 Li結尾
 "Alex\tLi".expandtabs(10) 輸出'Alex      Li'， 將\t轉換成多長的空格 
 name.find('A')  查詢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所在字串的索引
'9aA'.isalnum()   True

'9'.isdigit() 是否整數
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')   輸出 ('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 大小寫互換


 >>> 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() #檢測一段字串可否被當作標誌符，即是否符合變數命名規則
True

3. 字典操作

字典一種key - value 的資料型別，使用就像我們上學用的字典，通過筆劃、字母來查對應頁的詳細內容。

語法:

info = {
    'stu1101': "TengLan Wu",
    'stu1102': "LongZe Luola",
    'stu1103': "XiaoZe Maliya",
}

字典的特性：

• dict是無序的
• key必須是唯一的,so 天生去重

增加

修改

刪除

查詢

多級字典巢狀及操作

其它姿勢

迴圈dict

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

#方法2
for k,v in info.items(): #會先把dict轉成list,資料裡大時莫用
    print(k,v)

程式練習

程式: 三級選單

要求:

1. 列印省、市、縣三級選單
2. 可返回上一級
3. 可隨時退出程式

4.集合操作

集合是一個無序的，不重複的資料組合，它的主要作用如下：

• 去重，把一個列表變成集合，就自動去重了
• 關係測試，測試兩組資料之前的交集、差集、並集等關係

常用操作

5. 檔案操作

對檔案操作流程

1. 開啟檔案，得到檔案控制代碼並賦值給一個變數
2. 通過控制代碼對檔案進行操作
3. 關閉檔案

現有檔案如下

基本操作　　

開啟檔案的模式有：

• r，只讀模式（預設）。
• w，只寫模式。【不可讀；不存在則建立；存在則刪除內容；】
• a，追加模式。【可讀； 不存在則建立；存在則只追加內容；】

"+" 表示可以同時讀寫某個檔案

• r+，可讀寫檔案。【可讀；可寫；可追加】
• w+，寫讀
• a+，同a

"U"表示在讀取時，可以將 \r \n \r\n自動轉換成 \n （與 r 或 r+ 模式同使用）

• rU
• r+U

"b"表示處理二進位制檔案（如：FTP傳送上傳ISO映象檔案，linux可忽略，windows處理二進位制檔案時需標註）

• rb
• wb
• ab

其它語法

    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，不一定能全讀回來
        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,沒人知道它是幹嘛用的

    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語句

為了避免開啟檔案後忘記關閉，可以通過管理上下文，即：

如此方式，當with程式碼塊執行完畢時，內部會自動關閉並釋放檔案資源。

在Python 2.7 後，with又支援同時對多個檔案的上下文進行管理，即：

程式練習　　

程式1: 實現簡單的shell sed替換功能

程式2:修改haproxy配置檔案

需求：

6.字元編碼與轉碼

詳細文章:

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

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

需知:

1.在python2預設編碼是ASCII, python3裡預設是unicode

2.unicode 分為 utf-32(佔4個位元組),utf-16(佔兩個位元組)，utf-8(佔1-4個位元組)， so utf-16就是現在最常用的unicode版本， 不過在檔案裡存的還是utf-8，因為utf8省空間

3.在py3中encode,在轉碼的同時還會把string 變成bytes型別，decode在解碼的同時還會把bytes變回string

上圖僅適用於py2

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

import sys
print(sys.getdefaultencoding())


msg = "我愛北京天安門"
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)

#-*-coding:gb2312 -*-   #這個也可以去掉
__author__ = 'Alex Li'

import sys
print(sys.getdefaultencoding())


msg = "我愛北京天安門"
#msg_gb2312 = msg.decode("utf-8").encode("gb2312")
msg_gb2312 = msg.encode("gb2312") #預設就是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)

7. 內建函式

上圖僅適用於py2