Python基础2

本节内容

1. 列表、元组操作
2. 字符串操作
3. 字典操作
4. 集合操作
5. 文件操作
6. 字符编码与转码

names = ["a","b","c","d","e","f"]
names.append('gushiren') #添加

names.insert(2,'kilo')  #从b后面插入
names.insert(5,'juno')  #从e后面插入

names[2] = 'icehouse'   #修改del names[2]    #删除
names.remove('kilo') #删除指定元素
names.pop()　　#删除最后一个元素

b = [1,2,3]
names.extend(b)   #拓展

names.count("juno")  #统计
names.sort()  #排序
names.reverse() #翻转names.index('kilo') #获取下标

#切片，取多个元素
>>> names = ["a","b","c","d","e","f"]
>>> names[1:4]  #取下标1至下标4之间的数字，包括1，不包括4
['b', 'c', 'd']
>>> names[1:-1] #取下标1至-1的值，不包括-1
['b', 'c', 'd', 'e']
>>> names[0:3] 
['a', 'b', 'c']
>>> names[:3] #如果是从头开始取，0可以忽略，跟上句效果一样
['a', 'b', 'c']
>>> names[3:] #如果想取最后一个，必须不能写-1，只能这么写
['d', 'e', 'f']
>>> names[3:-1] #这样-1就不会被包含了
['d', 'e']
>>> names[0::2] #后面的2是代表，每隔一个元素，就取一个
['a', 'c', 'e']
>>> names[::2] #和上句效果一样
['a', 'c', 'e']

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

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	Li".expandtabs(10) 输出'Alex      Li'， 将	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

 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。