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python day2 python基础列表、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...

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本節(jié)內(nèi)容

列表、元組操作

字符串操作

字典操作

集合操作

文件操作

字符編碼與轉(zhuǎn)碼?

1. 列表、元組操作

列表是我們最以后最常用的數(shù)據(jù)類型之一，通過(guò)列表可以對(duì)數(shù)據(jù)實(shí)現(xiàn)最方便的存儲(chǔ)、修改等操作

定義列表

1 names = ['Alex',"Tenglan",'Eric']

通過(guò)下標(biāo)訪問(wèn)列表中的元素，下標(biāo)從0開(kāi)始計(jì)數(shù)

1 >>> names[0] 2 'Alex' 3 >>> names[2] 4 'Eric' 5 >>> names[-1] 6 'Eric' 7 >>> names[-2] #還可以倒著取 8 'Tenglan'

切片:取多個(gè)元素

1 >>> names = ["Alex","Tenglan","Eric","Rain","Tom","Amy"] 2 >>> names[1:4] #取下標(biāo)1至下標(biāo)4之間的數(shù)字，包括1，不包括4 3 ['Tenglan', 'Eric', 'Rain'] 4 >>> names[1:-1] #取下標(biāo)1至-1的值，不包括-1 5 ['Tenglan', 'Eric', 'Rain', 'Tom'] 6 >>> names[0:3] 7 ['Alex', 'Tenglan', 'Eric'] 8 >>> names[:3] #如果是從頭開(kāi)始取，0可以忽略，跟上句效果一樣 9 ['Alex', 'Tenglan', 'Eric'] 10 >>> names[3:] #如果想取最后一個(gè)，必須不能寫-1，只能這么寫 11 ['Rain', 'Tom', 'Amy'] 12 >>> names[3:-1] #這樣-1就不會(huì)被包含了 13 ['Rain', 'Tom'] 14 >>> names[0::2] #后面的2是代表，每隔一個(gè)元素，就取一個(gè) 15 ['Alex', 'Eric', 'Tom'] 16 >>> names[::2] #和上句效果一樣 17 ['Alex', 'Eric', 'Tom']

追加

1 >>> names 2 ['Alex', 'Tenglan', 'Eric', 'Rain', 'Tom', 'Amy'] 3 >>> names.append("我是新來(lái)的") 4 >>> names 5 ['Alex', 'Tenglan', 'Eric', 'Rain', 'Tom', 'Amy', '我是新來(lái)的']

插入

1 >>> names 2 ['Alex', 'Tenglan', 'Eric', 'Rain', 'Tom', 'Amy', '我是新來(lái)的'] 3 >>> names.insert(2,"強(qiáng)行從Eric前面插入") 4 >>> names 5 ['Alex', 'Tenglan', '強(qiáng)行從Eric前面插入', 'Eric', 'Rain', 'Tom', 'Amy', '我是新來(lái)的'] 6 7 >>> names.insert(5,"從eric后面插入試試新姿勢(shì)") 8 >>> names 9 ['Alex', 'Tenglan', '強(qiáng)行從Eric前面插入', 'Eric', 'Rain', '從eric后面插入試試新姿勢(shì)', 'Tom', 'Amy', '我是新來(lái)的']

修改

1 >>> names 2 ['Alex', 'Tenglan', '強(qiáng)行從Eric前面插入', 'Eric', 'Rain', '從eric后面插入試試新姿勢(shì)', 'Tom', 'Amy', '我是新來(lái)的'] 3 >>> names[2] = "該換人了" 4 >>> names 5 ['Alex', 'Tenglan', '該換人了', 'Eric', 'Rain', '從eric后面插入試試新姿勢(shì)', 'Tom', 'Amy', '我是新來(lái)的']

刪除

1 >>> del names[2] 2 >>> names 3 ['Alex', 'Tenglan', 'Eric', 'Rain', '從eric后面插入試試新姿勢(shì)', 'Tom', 'Amy', '我是新來(lái)的'] 4 >>> del names[4] 5 >>> names 6 ['Alex', 'Tenglan', 'Eric', 'Rain', 'Tom', 'Amy', '我是新來(lái)的'] 7 >>> 8 >>> names.remove("Eric") #刪除指定元素 9 >>> names 10 ['Alex', 'Tenglan', 'Rain', 'Tom', 'Amy', '我是新來(lái)的'] 11 >>> names.pop() #刪除列表最后一個(gè)值 12 '我是新來(lái)的' 13 >>> names 14 ['Alex', 'Tenglan', 'Rain', 'Tom', 'Amy']

擴(kuò)展

>>> names ['Alex', 'Tenglan', 'Rain', 'Tom', 'Amy'] >>> b = [1,2,3] >>> names.extend(b) >>> names ['Alex', 'Tenglan', 'Rain', 'Tom', 'Amy', 1, 2, 3]

拷貝

1 >>> names 2 ['Alex', 'Tenglan', 'Amy', 'Tom', 'Amy', 1, 2, 3] 3 >>> names.count("Amy") 4 2

排序&翻轉(zhuǎn)

1 >>> names 2 ['Alex', 'Tenglan', 'Amy', 'Tom', 'Amy', 1, 2, 3] 3 >>> names.sort() #排序 4 Traceback (most recent call last): 5 File "<stdin>", line 1, in <module> 6 TypeError: unorderable types: int() < str() #3.0里不同數(shù)據(jù)類型不能放在一起排序了，擦 7 >>> names[-3] = '1' 8 >>> names[-2] = '2' 9 >>> names[-1] = '3' 10 >>> names 11 ['Alex', 'Amy', 'Amy', 'Tenglan', 'Tom', '1', '2', '3'] 12 >>> names.sort() 13 >>> names 14 ['1', '2', '3', 'Alex', 'Amy', 'Amy', 'Tenglan', 'Tom'] 15 16 >>> names.reverse() #反轉(zhuǎn) 17 >>> names 18 ['Tom', 'Tenglan', 'Amy', 'Amy', 'Alex', '3', '2', '1']

獲取下標(biāo)

1 >>> names 2 ['Tom', 'Tenglan', 'Amy', 'Amy', 'Alex', '3', '2', '1'] 3 >>> names.index("Amy") 4 2 #只返回找到的第一個(gè)下標(biāo)

元組

元組其實(shí)跟列表差不多，也是存一組數(shù)，只不是它一旦創(chuàng)建，便不能再修改，所以又叫只讀列表

語(yǔ)法

1 names = ("alex","jack","eric")

它只有2個(gè)方法，一個(gè)是count,一個(gè)是index，完畢。　　

程序練習(xí)?

請(qǐng)閉眼寫出以下程序。

程序：購(gòu)物車程序

需求:

啟動(dòng)程序后，讓用戶輸入工資，然后打印商品列表

允許用戶根據(jù)商品編號(hào)購(gòu)買商品

用戶選擇商品后，檢測(cè)余額是否夠，夠就直接扣款，不夠就提醒?

可隨時(shí)退出，退出時(shí)，打印已購(gòu)買商品和余額

2. 字符串操作　

特性：不可修改　

1 name.capitalize() 首字母大寫 2 name.casefold() 大寫全部變小寫 3 name.center(50,"-") 輸出 '---------------------Alex Li----------------------' 4 name.count('lex') 統(tǒng)計(jì) lex出現(xiàn)次數(shù) 5 name.encode() 將字符串編碼成bytes格式 6 name.endswith("Li") 判斷字符串是否以 Li結(jié)尾 7 "Alex\tLi".expandtabs(10) 輸出'Alex Li'，將\t轉(zhuǎn)換成多長(zhǎng)的空格 8 name.find('A') 查找A,找到返回其索引，找不到返回-1 9 10 format : 11 >>> msg = "my name is {}, and age is {}" 12 >>> msg.format("alex",22) 13 'my name is alex, and age is 22' 14 >>> msg = "my name is {1}, and age is {0}" 15 >>> msg.format("alex",22) 16 'my name is 22, and age is alex' 17 >>> msg = "my name is {name}, and age is {age}" 18 >>> msg.format(age=22,name="ale") 19 'my name is ale, and age is 22' 20 format_map 21 >>> msg.format_map({'name':'alex','age':22}) 22 'my name is alex, and age is 22' 23 24 25 msg.index('a') 返回a所在字符串的索引 26 '9aA'.isalnum() True 27 28 '9'.isdigit() 是否整數(shù) 29 name.isnumeric 30 name.isprintable 31 name.isspace 32 name.istitle 33 name.isupper 34 "|".join(['alex','jack','rain']) 35 'alex|jack|rain' 36 37 38 maketrans 39 >>> intab = "aeiou" #This is the string having actual characters. 40 >>> outtab = "12345" #This is the string having corresponding mapping character 41 >>> trantab = str.maketrans(intab, outtab) 42 >>> 43 >>> str = "this is string example....wow!!!" 44 >>> str.translate(trantab) 45 'th3s 3s str3ng 2x1mpl2....w4w!!!' 46 47 msg.partition('is') 輸出 ('my name ', 'is', ' {name}, and age is {age}') 48 49 >>> "alex li, chinese name is lijie".replace("li","LI",1) 50 'alex LI, chinese name is lijie' 51 52 msg.swapcase 大小寫互換 53 54 55 >>> msg.zfill(40) 56 '00000my name is {name}, and age is {age}' 57 58 59 60 >>> n4.ljust(40,"-") 61 'Hello 2orld-----------------------------' 62 >>> n4.rjust(40,"-") 63 '-----------------------------Hello 2orld' 64 65 66 >>> b="ddefdsdff_哈哈" 67 >>> b.isidentifier() #檢測(cè)一段字符串可否被當(dāng)作標(biāo)志符，即是否符合變量命名規(guī)則 68 True

3. 字典操作

字典一種key - value 的數(shù)據(jù)類型，使用就像我們上學(xué)用的字典，通過(guò)筆劃、字母來(lái)查對(duì)應(yīng)頁(yè)的詳細(xì)內(nèi)容。

語(yǔ)法:

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

字典的特性：

dict是無(wú)序的
key必須是唯一的,so 天生去重

增加

>>> info["stu1104"] = "蒼井空" >>> info {'stu1102': 'LongZe Luola', 'stu1104': '蒼井空', 'stu1103': 'XiaoZe Maliya', 'stu1101': 'TengLan Wu'}

修改

>>> info['stu1101'] = "武藤蘭" >>> info {'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya', 'stu1101': '武藤蘭'}

刪除

>>> info {'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya', 'stu1101': '武藤蘭'} >>> info.pop("stu1101") #標(biāo)準(zhǔn)刪除姿勢(shì) '武藤蘭' >>> info {'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'} >>> del info['stu1103'] #換個(gè)姿勢(shì)刪除 >>> info {'stu1102': 'LongZe Luola'} >>> >>> >>> >>> info = {'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'} >>> info {'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'} #隨機(jī)刪除 >>> info.popitem() ('stu1102', 'LongZe Luola') >>> info {'stu1103': 'XiaoZe Maliya'}

查找

>>> info = {'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'} >>> >>> "stu1102" in info #標(biāo)準(zhǔn)用法 True >>> info.get("stu1102") #獲取 'LongZe Luola' >>> info["stu1102"] #同上，但是看下面 'LongZe Luola' >>> info["stu1105"] #如果一個(gè)key不存在，就報(bào)錯(cuò)，get不會(huì)，不存在只返回None Traceback (most recent call last):File "<stdin>", line 1, in <module> KeyError: 'stu1105'

多級(jí)字典嵌套及操作

av_catalog = {"歐美":{"www.youporn.com": ["很多免費(fèi)的,世界最大的","質(zhì)量一般"],"www.pornhub.com": ["很多免費(fèi)的,也很大","質(zhì)量比yourporn高點(diǎn)"],"letmedothistoyou.com": ["多是自拍,高質(zhì)量圖片很多","資源不多,更新慢"],"x-art.com":["質(zhì)量很高,真的很高","全部收費(fèi),屌比請(qǐng)繞過(guò)"]},"日韓":{"tokyo-hot":["質(zhì)量怎樣不清楚,個(gè)人已經(jīng)不喜歡日韓范了","聽(tīng)說(shuō)是收費(fèi)的"]},"大陸":{"1024":["全部免費(fèi),真好,好人一生平安","服務(wù)器在國(guó)外,慢"]} }av_catalog["大陸"]["1024"][1] += ",可以用爬蟲(chóng)爬下來(lái)" print(av_catalog["大陸"]["1024"]) #ouput ['全部免費(fèi),真好,好人一生平安', '服務(wù)器在國(guó)外,慢,可以用爬蟲(chóng)爬下來(lái)']

其它姿勢(shì)

#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","龍澤蘿拉") '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":"龍澤蘿拉"} >>> info.update(b) >>> info {'stu1102': '龍澤蘿拉', 1: 2, 3: 4, 'stu1103': 'XiaoZe Maliya', 'stu1106': 'Alex'}#items info.items() dict_items([('stu1102', '龍澤蘿拉'), (1, 2), (3, 4), ('stu1103', 'XiaoZe Maliya'), ('stu1106', 'Alex')])#通過(guò)一個(gè)列表生成默認(rèn)dict,有個(gè)沒(méi)辦法解釋的坑，少用吧這個(gè) >>> dict.fromkeys([1,2,3],'testd') {1: 'testd', 2: 'testd', 3: 'testd'}

循環(huán)dict?

#方法1 for key in info:print(key,info[key])#方法2 for k,v in info.items(): #會(huì)先把dict轉(zhuǎn)成list,數(shù)據(jù)里大時(shí)莫用print(k,v)

程序練習(xí)

程序: 三級(jí)菜單

要求:?

打印省、市、縣三級(jí)菜單

可返回上一級(jí)

可隨時(shí)退出程序

menu = {'北京':{'海淀':{'五道口':{'soho':{},'網(wǎng)易':{},'google':{}},'中關(guān)村':{'愛(ài)奇藝':{},'汽車之家':{},'youku':{},},'上地':{'百度':{},},},'昌平':{'沙河':{'老男孩':{},'北航':{},},'天通苑':{},'回龍觀':{},},'朝陽(yáng)':{},'東城':{},},'上海':{'閔行':{"人民廣場(chǎng)":{'炸雞店':{}}},'閘北':{'火車戰(zhàn)':{'攜程':{}}},'浦東':{},},'山東':{}, }exit_flag = False current_layer = menulayers = [menu]while not exit_flag:for k in current_layer:print(k)choice = input(">>:").strip()if choice == "b":current_layer = layers[-1]#print("change to laster", current_layer) layers.pop()elif choice not in current_layer:continueelse:layers.append(current_layer)current_layer = current_layer[choice]

4.集合操作

集合是一個(gè)無(wú)序的，不重復(fù)的數(shù)據(jù)組合，它的主要作用如下：

去重，把一個(gè)列表變成集合，就自動(dòng)去重了
關(guān)系測(cè)試，測(cè)試兩組數(shù)據(jù)之前的交集、差集、并集等關(guān)系

常用操作

s = set([3,5,9,10]) #創(chuàng)建一個(gè)數(shù)值集合 t = set("Hello") #創(chuàng)建一個(gè)唯一字符的集合 a = t | s # t 和 s的并集 b = t & s # t 和 s的交集 c = t – s # 求差集（項(xiàng)在t中，但不在s中） d = t ^ s # 對(duì)稱差集（項(xiàng)在t或s中，但不會(huì)同時(shí)出現(xiàn)在二者中）基本操作： t.add('x') # 添加一項(xiàng) s.update([10,37,42]) # 在s中添加多項(xiàng) 使用remove()可以刪除一項(xiàng)： t.remove('H') len(s) set 的長(zhǎng)度 x in s 測(cè)試 x 是否是 s 的成員 x not in s 測(cè)試 x 是否不是 s 的成員 s.issubset(t) s <= t 測(cè)試是否 s 中的每一個(gè)元素都在 t 中 s.issuperset(t) s >= t 測(cè)試是否 t 中的每一個(gè)元素都在 s 中 s.union(t) s | t 返回一個(gè)新的 set 包含 s 和 t 中的每一個(gè)元素 s.intersection(t) s & t 返回一個(gè)新的 set 包含 s 和 t 中的公共元素 s.difference(t) s - t 返回一個(gè)新的 set 包含 s 中有但是 t 中沒(méi)有的元素 s.symmetric_difference(t) s ^ t 返回一個(gè)新的 set 包含 s 和 t 中不重復(fù)的元素 s.copy() 返回 set “s”的一個(gè)淺復(fù)制

5. 文件操作

對(duì)文件操作流程

打開(kāi)文件，得到文件句柄并賦值給一個(gè)變量

通過(guò)句柄對(duì)文件進(jìn)行操作

關(guān)閉文件?

現(xiàn)有文件如下?

1 Somehow, it seems the love I knew was always the most destructive kind 2 不知為何，我經(jīng)歷的愛(ài)情總是最具毀滅性的的那種 3 Yesterday when I was young 4 昨日當(dāng)我年少輕狂 5 The taste of life was sweet 6 生命的滋味是甜的 7 As rain upon my tongue 8 就如舌尖上的雨露 9 I teased at life as if it were a foolish game 10 我戲弄生命視其為愚蠢的游戲 11 The way the evening breeze 12 就如夜晚的微風(fēng) 13 May tease the candle flame 14 逗弄蠟燭的火苗 15 The thousand dreams I dreamed 16 我曾千萬(wàn)次夢(mèng)見(jiàn) 17 The splendid things I planned 18 那些我計(jì)劃的絢麗藍(lán)圖 19 I always built to last on weak and shifting sand 20 但我總是將之建筑在易逝的流沙上 21 I lived by night and shunned the naked light of day 22 我夜夜笙歌逃避白晝赤裸的陽(yáng)光 23 And only now I see how the time ran away 24 事到如今我才看清歲月是如何匆匆流逝 25 Yesterday when I was young 26 昨日當(dāng)我年少輕狂 27 So many lovely songs were waiting to be sung 28 有那么多甜美的曲兒等我歌唱 29 So many wild pleasures lay in store for me 30 有那么多肆意的快樂(lè)等我享受 31 And so much pain my eyes refused to see 32 還有那么多痛苦我的雙眼卻視而不見(jiàn) 33 I ran so fast that time and youth at last ran out 34 我飛快地奔走最終時(shí)光與青春消逝殆盡 35 I never stopped to think what life was all about 36 我從未停下腳步去思考生命的意義 37 And every conversation that I can now recall 38 如今回想起的所有對(duì)話 39 Concerned itself with me and nothing else at all 40 除了和我相關(guān)的什么都記不得了 41 The game of love I played with arrogance and pride 42 我用自負(fù)和傲慢玩著愛(ài)情的游戲 43 And every flame I lit too quickly, quickly died 44 所有我點(diǎn)燃的火焰都熄滅得太快 45 The friends I made all somehow seemed to slip away 46 所有我交的朋友似乎都不知不覺(jué)地離開(kāi)了 47 And only now I'm left alone to end the play, yeah 48 只剩我一個(gè)人在臺(tái)上來(lái)結(jié)束這場(chǎng)鬧劇 49 Oh, yesterday when I was young 50 噢昨日當(dāng)我年少輕狂 51 So many, many songs were waiting to be sung 52 有那么那么多甜美的曲兒等我歌唱 53 So many wild pleasures lay in store for me 54 有那么多肆意的快樂(lè)等我享受 55 And so much pain my eyes refused to see 56 還有那么多痛苦我的雙眼卻視而不見(jiàn) 57 There are so many songs in me that won't be sung 58 我有太多歌曲永遠(yuǎn)不會(huì)被唱起 59 I feel the bitter taste of tears upon my tongue 60 我嘗到了舌尖淚水的苦澀滋味 61 The time has come for me to pay for yesterday 62 終于到了付出代價(jià)的時(shí)間為了昨日 63 When I was young 64 當(dāng)我年少輕狂

基本操作　

1 f = open('lyrics') #打開(kāi)文件 2 first_line = f.readline() 3 print('first line:',first_line) #讀一行 4 print('我是分隔線'.center(50,'-')) 5 data = f.read()# 讀取剩下的所有內(nèi)容,文件大時(shí)不要用 6 print(data) #打印文件 7 8 f.close() #關(guān)閉文件

打開(kāi)文件的模式有：

r，只讀模式（默認(rèn)）。
w，只寫模式。【不可讀；不存在則創(chuàng)建；存在則刪除內(nèi)容；】
a，追加模式。【可讀； ? 不存在則創(chuàng)建；存在則只追加內(nèi)容；】

"+" 表示可以同時(shí)讀寫某個(gè)文件

r+，可讀寫文件。【可讀；可寫；可追加】
w+，寫讀
a+，同a

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

"b"表示處理二進(jìn)制文件（如：FTP發(fā)送上傳ISO鏡像文件，linux可忽略，windows處理二進(jìn)制文件時(shí)需標(biāo)注）

其它語(yǔ)法

1 def close(self): # real signature unknown; restored from __doc__ 2 """ 3 Close the file. 4 5 A closed file cannot be used for further I/O operations. close() may be 6 called more than once without error. 7 """ 8 pass 9 10 def fileno(self, *args, **kwargs): # real signature unknown 11 """ Return the underlying file descriptor (an integer). """ 12 pass 13 14 def isatty(self, *args, **kwargs): # real signature unknown 15 """ True if the file is connected to a TTY device. """ 16 pass 17 18 def read(self, size=-1): # known case of _io.FileIO.read 19 """ 20 注意，不一定能全讀回來(lái) 21 Read at most size bytes, returned as bytes. 22 23 Only makes one system call, so less data may be returned than requested. 24 In non-blocking mode, returns None if no data is available. 25 Return an empty bytes object at EOF. 26 """ 27 return "" 28 29 def readable(self, *args, **kwargs): # real signature unknown 30 """ True if file was opened in a read mode. """ 31 pass 32 33 def readall(self, *args, **kwargs): # real signature unknown 34 """ 35 Read all data from the file, returned as bytes. 36 37 In non-blocking mode, returns as much as is immediately available, 38 or None if no data is available. Return an empty bytes object at EOF. 39 """ 40 pass 41 42 def readinto(self): # real signature unknown; restored from __doc__ 43 """ Same as RawIOBase.readinto(). """ 44 pass #不要用,沒(méi)人知道它是干嘛用的 45 46 def seek(self, *args, **kwargs): # real signature unknown 47 """ 48 Move to new file position and return the file position. 49 50 Argument offset is a byte count. Optional argument whence defaults to 51 SEEK_SET or 0 (offset from start of file, offset should be >= 0); other values 52 are SEEK_CUR or 1 (move relative to current position, positive or negative), 53 and SEEK_END or 2 (move relative to end of file, usually negative, although 54 many platforms allow seeking beyond the end of a file). 55 56 Note that not all file objects are seekable. 57 """ 58 pass 59 60 def seekable(self, *args, **kwargs): # real signature unknown 61 """ True if file supports random-access. """ 62 pass 63 64 def tell(self, *args, **kwargs): # real signature unknown 65 """ 66 Current file position. 67 68 Can raise OSError for non seekable files. 69 """ 70 pass 71 72 def truncate(self, *args, **kwargs): # real signature unknown 73 """ 74 Truncate the file to at most size bytes and return the truncated size. 75 76 Size defaults to the current file position, as returned by tell(). 77 The current file position is changed to the value of size. 78 """ 79 pass 80 81 def writable(self, *args, **kwargs): # real signature unknown 82 """ True if file was opened in a write mode. """ 83 pass 84 85 def write(self, *args, **kwargs): # real signature unknown 86 """ 87 Write bytes b to file, return number written. 88 89 Only makes one system call, so not all of the data may be written. 90 The number of bytes actually written is returned. In non-blocking mode, 91 returns None if the write would block. 92 """ 93 pass

with語(yǔ)句

為了避免打開(kāi)文件后忘記關(guān)閉，可以通過(guò)管理上下文，即：

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

如此方式，當(dāng)with代碼塊執(zhí)行完畢時(shí)，內(nèi)部會(huì)自動(dòng)關(guān)閉并釋放文件資源。

在Python 2.7 后，with又支持同時(shí)對(duì)多個(gè)文件的上下文進(jìn)行管理，即：

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

程序練習(xí)　　

程序1: 實(shí)現(xiàn)簡(jiǎn)單的shell sed替換功能

程序2:修改haproxy配置文件?

需求：

1、查輸入：www.oldboy.org獲取當(dāng)前backend下的所有記錄2、新建輸入：arg = {'bakend': 'www.oldboy.org','record':{'server': '100.1.7.9','weight': 20,'maxconn': 30}}3、刪除輸入：arg = {'bakend': 'www.oldboy.org','record':{'server': '100.1.7.9','weight': 20,'maxconn': 30}} global log 127.0.0.1 local2daemonmaxconn 256log 127.0.0.1 local2 info defaultslog globalmode httptimeout connect 5000mstimeout client 50000mstimeout server 50000msoption dontlognulllisten stats :8888stats enablestats uri /adminstats auth admin:1234frontend oldboy.orgbind 0.0.0.0:80option httplogoption httpcloseoption forwardforlog globalacl www hdr_reg(host) -i www.oldboy.orguse_backend www.oldboy.org if wwwbackend www.oldboy.orgserver 100.1.7.9 100.1.7.9 weight 20 maxconn 3000 原配置文件

6.?字符編碼與轉(zhuǎn)碼

詳細(xì)文章:

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

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

需知:

1.在python2默認(rèn)編碼是ASCII, python3里默認(rèn)是unicode

2.unicode 分為 utf-32(占4個(gè)字節(jié)),utf-16(占兩個(gè)字節(jié))，utf-8(占1-4個(gè)字節(jié))， so utf-16就是現(xiàn)在最常用的unicode版本，不過(guò)在文件里存的還是utf-8，因?yàn)閡tf8省空間

3.在py3中encode,在轉(zhuǎn)碼的同時(shí)還會(huì)把string 變成bytes類型，decode在解碼的同時(shí)還會(huì)把bytes變回string

?上圖僅適用于py2

#-*-coding:utf-8-*- __author__ = 'Alex Li'import sys print(sys.getdefaultencoding())msg = "我愛(ài)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(gè)也可以去掉 __author__ = 'Alex Li'import sys print(sys.getdefaultencoding())msg = "我愛(ài)北京天安門" #msg_gb2312 = msg.decode("utf-8").encode("gb2312") msg_gb2312 = msg.encode("gb2312") #默認(rèn)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(nèi)置函數(shù)

轉(zhuǎn)載于:https://www.cnblogs.com/xyyhcn/p/10199547.html