02 - Python 基础

一、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

1、定义列表:

names = ["Ben", "Nicole", "Dingding"]

通过下标访问列表中的元素，下标从0开始计数

print(names[0])
print(names[2])
print(names[-1])
print(names[-2])

结果：

Ben
Dingding
Dingding
Nicole

2、切片:取多个元素:

names = ["Ben","Nicole","Dingding","Rain","Tom","Amy"]
print("[names]: %s" % names)
print("names[1:4]: %s" % names[1:4]) # 取下标1至下标4之间的数字，包括1，不包括4
print("names[1:-1]: %s" % names[1:-1]) # 取下标1至-1的值，不包括-1
print("names[0:3]: %s" % names[0:3]) # 取下标0至3的值，不包括3
print("names[:3]: %s" % names[:3]) # 如果是从头开始取，0可以忽略，跟上句效果一样
print("names[3:]: %s" % names[3:]) # 如果想取最后一个，必须不能写-1，只能这么写
print("names[3:-1]: %s" % names[3:-1]) # 这样-1就不会被包含了
print("names[0::2]: %s" % names[0::2]) # 后面的2是代表，每隔一个元素，就取一个
print("names[::2]: %s" % names[::2]) # 和上句效果一样

结果：

[names]: ['Ben', 'Nicole', 'Dingding', 'Rain', 'Tom', 'Amy']
names[1:4]: ['Nicole', 'Dingding', 'Rain']
names[1:-1]: ['Nicole', 'Dingding', 'Rain', 'Tom']
names[0:3]: ['Ben', 'Nicole', 'Dingding']
names[:3]: ['Ben', 'Nicole', 'Dingding']
names[3:]: ['Rain', 'Tom', 'Amy']
names[3:-1]: ['Rain', 'Tom']
names[0::2]: ['Ben', 'Dingding', 'Tom']
names[::2]: ['Ben', 'Dingding', 'Tom']

3、追加

names.append("我是新来的") # 追加
print(names)

结果：

['Ben', 'Nicole', 'Dingding', 'Rain', 'Tom', 'Amy', '我是新来的']

4、插入

names.insert(2, "从Nicole后面插入") # 插入
print(names)
names.insert(5, "从Rain后面插入") # 插入
print(names)

结果：

['Ben', 'Nicole', '从Nicole后面插入', 'Dingding', 'Rain', 'Tom', 'Amy']
['Ben', 'Nicole', '从Nicole后面插入', 'Dingding', 'Rain', '从Rain后面插入', 'Tom', 'Amy']

5、修改

names[2] = "该换人了" # 修改
print(names)

结果：

['Ben', 'Nicole', '该换人了', 'Dingding', 'Rain', '从Rain后面插入', 'Tom', 'Amy', '我是新来的']

6、删除

del names[2] # 删除
print(names)
del names[4] # 删除
print(names)
names.remove("Rain") # 删除指定元数
print(names)
names.pop() # 删除列表最后一个值 '我是新来的'
print(names)

结果：

['Ben', 'Nicole', 'Dingding', 'Rain', '从Rain后面插入', 'Tom', 'Amy', '我是新来的']
['Ben', 'Nicole', 'Dingding', 'Rain', 'Tom', 'Amy', '我是新来的']
['Ben', 'Nicole', 'Dingding', 'Tom', 'Amy', '我是新来的']
['Ben', 'Nicole', 'Dingding', 'Tom', 'Amy']

7、扩展

names = ["Ben","Nicole","Dingding","Rain","Tom","Amy"]
b = [1, 2, 3]
names.extend(b) # 扩展
print(names)

结果：

['Ben', 'Nicole', 'Dingding', 'Rain', 'Tom', 'Amy', 1, 2, 3]

8、拷贝

print(names)
names_copy = names.copy() # 拷贝
print(names_copy)

结果：

['Ben', 'Nicole', 'Dingding', 'Rain', 'Tom', 'Amy', 1, 2, 3]
['Ben', 'Nicole', 'Dingding', 'Rain', 'Tom', 'Amy', 1, 2, 3]

9、统计

names = ["Ben","Nicole","Dingding","Rain","Dingding","Amy"]
print(names.count("Dingding")) # 统计

结果：

2

10、排序&翻转

names = ["Ben","Nicole","Dingding","Rain","Dingding","Amy", 1, 2, 3]
print(names.sort()) # 排序

结果：

Traceback (most recent call last):
File "/Users/benzhong/Ben/Study/codes/Python_Basic/02/列表操作.py", line 45, in

print(names.sort()) # 排序

TypeError: unorderable types: int() < str()

3.0里不同数据类型不能放在一起排序了

names = ["Ben","Nicole","Dingding","Rain","Dingding","Amy", 1, 2, 3]
names[-3] = "1"
names[-2] = "2"
names[-1] = "3"
print(names)
names.sort() # 排序
print(names)
names.reverse() # 反转
print(names)

结果：

['Ben', 'Nicole', 'Dingding', 'Rain', 'Dingding', 'Amy', '1', '2', '3']
['1', '2', '3', 'Amy', 'Ben', 'Dingding', 'Dingding', 'Nicole', 'Rain']
['Rain', 'Nicole', 'Dingding', 'Dingding', 'Ben', 'Amy', '3', '2', '1']

11、获取下标

names = ['Rain', 'Nicole', 'Dingding', 'Dingding', 'Ben', 'Amy', '3', '2', '1']
print(names.index("Nicole"))

结果：

1

12、元组

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

names = ("Ben", "Nicole", "Dingding")
print(type(names))
print(dir(names))

结果：

['add', 'class', 'contains', 'delattr', 'dir', 'doc', 'eq', 'format', 'ge', 'getattribute', 'getitem', 'getnewargs', 'gt', 'hash', 'init', 'iter', 'le', 'len', 'lt', 'mul', 'ne', 'new', 'reduce', 'reduce_ex', 'repr', 'rmul', 'setattr', 'sizeof', 'str', 'subclasshook', 'count', 'index']

它只有2个方法，一个是count,一个是index

13、程序练习

程序练习

请闭眼写出以下程序。
程序：购物车程序
需求:
启动程序后，让用户输入工资，然后打印商品列表
允许用户根据商品编号购买商品
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
可随时退出，退出时，打印已购买商品和余额

二、字符串操作

特性：不可修改

print("ben".capitalize()) # 首字母大写 Ben
print("bEn".swapcase()) # 交换大小写 BeN
print("ben".center(50, "-")) # -----------------------ben------------------------
print("benben".count("en")) # 统计 en 出现次数 2
print("ben".encode()) # 将字符串编码成bytes格式 b'ben'
print("abcdefghi".endswith("gh")) # 判断字符串是否以 gh结尾 False
print("abcdefghi".endswith("hi")) # 判断字符串是否以 hi结尾 True
print("abc\tben".expandtabs(10)) # 输出'abc       ben'， 将\t转换成多长的空格
print("ben".find("A")) # 查找A,找到返回其索引， 找不到返回-1 -1
print("ben".find("n")) # 查找A,找到返回其索引， 找不到返回-1 2

结果：

Ben
BeN
-----------------------ben------------------------
2
b'ben'
False
True
abc ben
-1
2

format:

msg = "my name is {}, and age is {}"
print(msg.format("ben", 18))
msg = "my name is {1}, and age is {0}"
print(msg.format("ben", 18))
msg = "my name is {name}, and age is {age}"
print(msg.format(age=18, name="ben"))
msg.format_map({'name':'ben', 'age':18})

结果：

my name is ben, and age is 18
my name is 18, and age is ben
my name is ben, and age is 18

华丽的分割线----------------------------------------------------------

msg = "my name is ben, and age is 18"
print(msg.index("a"))
print("9aA".isalnum())  # Return True if all characters in "9aA" are alphanumeric True
print('9'.isdigit())  # Return True if all characters in '9' are digitsTrue
print("Ben".isnumeric())  # Return True if there are only numeric characters in "Ben" False
print("ben ben".isprintable())  # Return True if all characters in "ben ben" are considered True
print("ben ben".isspace())  # Return True if all characters in ben ben are whitespace False
print("Ben".istitle())  # Return True if S is a titlecased string True
print("bEn".isupper())  # Return True if all cased characters in "bEn" are uppercase False
print("|".join(["Ben", "Nicole", "Dingding"]))

结果：

4
True
True
False
True
False
True
False
Ben|Nicole|Dingding

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!!!"
print(str.translate(trantab))

结果：

th3s 3s str3ng 2x1mpl2....w4w!!!

华丽的分割线----------------------------------------------------------

msg = "My name is Ben, and AGE is 18"
print(msg.partition("is"))
print(msg.partition(" "))

print(msg.swapcase())  # 大小写互换

print(len(msg))
print(msg.zfill(30))
print(msg.zfill(40))

print(msg.ljust(40, "-"))
print(msg.rjust(40, "*"))

b = "ddefdsdff_哈哈"
print(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

结果：

('My name ', 'is', ' Ben, and AGE is 18')
('My', ' ', 'name is Ben, and AGE is 18')
mY NAME IS bEN, AND age IS 18
29
0My name is Ben, and AGE is 18
00000000000My name is Ben, and AGE is 18
My name is Ben, and AGE is 18-----------
***********My name is Ben, and AGE is 18

True

三、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": "Ben ZHONG",
    "stu1102": "Nicole LIANG",
    "stu1103": "Dingding ZHONG",
}

字典的特性：

dict是无序的
key必须是唯一的,so 天生去重

1、增加

info["stu1104"] = "苍井空"  # 增加

结果：

{'stu1101': 'TengLan Wu', 'stu1104': '苍井空', 'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'}

2、修改

info["stu1101"] = "武藤兰"  # 修改

结果：

{'stu1101': '武藤兰', 'stu1104': '苍井空', 'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'}

3、删除

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

info.pop("stu1101")  # 标准删除姿势
print(info)
del info["stu1103"]  # 换个姿势删除
print(info)

结果：

{'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'}
{'stu1102': 'LongZe Luola'}

华丽的分割线----------------------------------------------------------

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

info.popitem()  # 随机删除
print(info)

结果：

{'stu1101': 'TengLan Wu', 'stu1103': 'XiaoZe Maliya'}

4、查找

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

print("stu1102" in info)  # 标准用法
print(info.get("stu1102"))  # 获取
print(info["stu1102"])  # 同上

结果：

True
LongZe Luola
LongZe Luola

华丽的分割线----------------------------------------------------------

print(info["stu1105"])  # 如果一个key不存在，就报错，get不会，不存在只返回None

结果：

Traceback (most recent call last):
File "/Users/benzhong/Ben/Study/codes/Python_Basic/02/字典操作.py", line 31, in
print(info["stu1105"]) # 如果一个key不存在，就报错，get不会，不存在只返回None
KeyError: 'stu1105'

华丽的分割线----------------------------------------------------------

print(info.get("stu1105"))  # 获取 get不会，不存在只返回None

结果：

None

5、多级字典嵌套及操作

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"])

结果：

['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']

6、其它知识

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

print("values:", info.values())  # values
print("keys:", info.keys())  # keys

# setdefault
info.setdefault("stu1106", "Ben")
print("setdefault:", info)

info.setdefault("stu1102","龙泽萝拉")  # 存在"stu1102" key 就不做任何操作
info.setdefault("stu1107","龙泽萝拉")  # 不存在"stu1102"，setdefault
print("setdefault:", info)

b = {1:2,3:4, "stu1102":"龙泽萝拉"}  # update
info.update(b)
print("update:", info)

print("items:", info.items())  # items

结果：

values: dict_values(['TengLan Wu', 'LongZe Luola', 'XiaoZe Maliya'])
keys: dict_keys(['stu1101', 'stu1102', 'stu1103'])
setdefault: {'stu1101': 'TengLan Wu', 'stu1102': 'LongZe Luola', 'stu1106': 'Ben', 'stu1103': 'XiaoZe Maliya'}
setdefault: {'stu1101': 'TengLan Wu', 'stu1102': 'LongZe Luola', 'stu1107': '龙泽萝拉', 'stu1106': 'Ben', 'stu1103': 'XiaoZe Maliya'}
update: {'stu1101': 'TengLan Wu', 1: 2, 3: 4, 'stu1103': 'XiaoZe Maliya', 'stu1102': '龙泽萝拉', 'stu1107': '龙泽萝拉', 'stu1106': 'Ben'}
items: dict_items([('stu1106', 'Ben'), (1, 2), (3, 4), ('stu1102', '龙泽萝拉'), ('stu1103', 'XiaoZe Maliya'), ('stu1107', '龙泽萝拉'), ('stu1101', 'TengLan Wu')])

7、循环dict

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

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

print()

# 方法2
print("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)

结果：

方法1
stu1101 TengLan Wu
stu1102 LongZe Luola
stu1103 XiaoZe Maliya

方法2
stu1101 TengLan Wu
stu1102 LongZe Luola
stu1103 XiaoZe Maliya

8、程序练习

程序: 三级菜单
要求:
打印省、市、县三级菜单
可返回上一级
可随时退出程序

四、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

s = set([3, 5, 9, 10])  # 创建一个数值集合
t = set("Hello")  # 创建一个唯一字符的集合

a = t | s  # t 和 s的并集
b = t & s  # t 和 s的交集
c = t - s  # 求差集（项在t中，但不在s中）
d = t ^ s  # 对称差集（项在t或s中，但不会同时出现在二者中）
print("a:", a)
print("b:", b)
print("c:", c)
print("d:", d)

结果：

a: {'e', 3, 5, 9, 10, 'o', 'H', 'l'}
b: set()
c: {'H', 'e', 'o', 'l'}
d: {3, 'e', 5, 9, 10, 'o', 'H', 'l'}

# 基本操作：
s = set([3, 5, 9, 10])  # 创建一个数值集合
t = set("Hello")  # 创建一个唯一字符的集合
t.add("x")  # 添加一项
s.update([10, 37, 42])  # 在s中添加多项
print("t:", t)
print("s:", s)

结果：

{'e', 'o', 'l', 'x', 'H'}
{3, 37, 5, 9, 10, 42}

s = set([3, 5, 9, 10])  # 创建一个数值集合
t = set("Hello")  # 创建一个唯一字符的集合
x = 5

print("t.remove('H'):", t.remove("H"))  # 使用remove()可以删除一项
print("len(s):", len(s))  # s set 的长度
print("x in s:", x in s)  # 测试 x 是否是 s 的成员
print("x not in s:", x not in s)  # 测试 x 是否不是 s 的成员
print("s.issubset(t):", s.issubset(t))  # 测试是否 s 中的每一个元素都在 t 中
print("s <= t:", s <= t)  # 测试是否 s 中的每一个元素都在 t 中
print("s.union(t):", s.union(t))  # 返回一个新的 set 包含 s 和 t 中的每一个元素
print("s | t:", s | t)  # 返回一个新的 set 包含 s 和 t 中的每一个元素
print("s.intersection(t):", s.intersection(t))  # 返回一个新的 set 包含 s 和 t 中的公共元素
print("s & t:", s & t)  # 返回一个新的 set 包含 s 和 t 中的公共元素
print("s.difference(t):", s.difference(t))  #  返回一个新的 set 包含 s 中有但是 t 中没有的元素
print("s - t:", s - t)  # 返回一个新的 set 包含 s 中有但是 t 中没有的元素
print("s.symmetric_difference(t):", s.symmetric_difference(t))  # 返回一个新的 set 包含 s 和 t 中不重复的元素
print("s ^ t:", s ^ t)  # 返回一个新的 set 包含 s 和 t 中不重复的元素
print("s.copy():", s.copy())  # 返回 set “s”的一个浅复制

结果：

t.remove('H'): None
len(s): 4
x in s: True
x not in s: False
s.issubset(t): False
s <= t: False
s.union(t): {3, 5, 'o', 9, 10, 'e', 'l'}
s | t: {3, 5, 'o', 9, 10, 'e', 'l'}
s.intersection(t): set()
s & t: set()
s.difference(t): {9, 10, 3, 5}
s - t: {9, 10, 3, 5}
s.symmetric_difference(t): {3, 5, 9, 10, 'l', 'e', 'o'}
s ^ t: {3, 5, 9, 10, 'l', 'e', 'o'}
s.copy(): {9, 10, 3, 5}

五、文件操作

1、对文件操作流程

打开文件，得到文件句柄并赋值给一个变量
通过句柄对文件进行操作
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

2、基本操作

f = open('lyrics')  # 打开文件
first_line = f.readline()
print('first line:', first_line)  # 读一行
print('我是分割线'.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）

3、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

4、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：

with open('log', 'r') as f:
    for line in f.readlines():
        print(line)

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：

with open('lyrics') as obj1, open('log') as obj2:
    pass

5、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
            }
        }

需求

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

原配置文件

六、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:

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

image.png

import sys
print(sys.getdefaultencoding())

msg = "python字符编码与转码"  # msg: utf-8
msg_gb2312 = msg.encode("gb2312")  # msg_gb2312: gb2312

# gb2312 to utf-8 需要通用unicode作中介转换
gb2312_to_unicode = msg_gb2312.decode("gb2312")  # gb2312_to_unicode: msg_gb2312由"gb2312" 转为"unicode"
gb2312_to_utf8 = msg_gb2312.decode("gb2312").encode("utf-8")  # gb2312_to_utf8: msg_gb2312由"gb2312" 先转为"unicode"，再转为utf-8

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

结果：

utf-8
python字符编码与转码
b'python\xd7\xd6\xb7\xfb\xb1\xe0\xc2\xeb\xd3\xeb\xd7\xaa\xc2\xeb'
python字符编码与转码
b'python\xe5\xad\x97\xe7\xac\xa6\xe7\xbc\x96\xe7\xa0\x81\xe4\xb8\x8e\xe8\xbd\xac\xe7\xa0\x81'

02 - Python 基础

一、列表、元组操作

1、定义列表:

2、切片:取多个元素:

3、追加

4、插入

5、修改

6、删除

7、扩展

8、拷贝

9、统计

10、排序&翻转

11、获取下标

12、元组

13、程序练习

二、字符串操作

特性：不可修改

format:

华丽的分割线----------------------------------------------------------

maketrans

华丽的分割线----------------------------------------------------------

三、字典操作

1、增加

2、修改

3、删除

华丽的分割线----------------------------------------------------------

4、查找

华丽的分割线----------------------------------------------------------

华丽的分割线----------------------------------------------------------

5、多级字典嵌套及操作

6、其它知识

7、循环dict

8、程序练习

四、集合操作

五、文件操作

1、对文件操作流程

2、基本操作

3、其它语法

4、with 语句

5、程序练习

六、字符编码与转码

你可能感兴趣的:(02 - Python 基础)