Automated DAY3---python basics (list, dictionaries, tuples, file read and write, string formatting)

1.list

Operation of List

#数组---list array
Stus = [' Xiaohei ', ' Xiaobai ', ' Xiaolan ']
#计算机取值是从0开始的
#0 1 2 3
#下标 angle index refers to a thing
#走后一个值可以用-to indicate
Print (stus[2]) #取第三个值
Print (stus[-1]) #取第三个值

#list的增删改查
#增
#append方法是在list末尾增加, you can only add one at a time
Stus.append (' YBQ ')
Print (Stus)
#insert方法是在指定位置增加
Stus.insert (0, ' MPP ') #0是位置
Print (Stus)
#如果指定的下标不存在, then it is added at the end
Stus.insert (9, ' MPP ') #9是位置, but does not exist
Print (Stus)

#改
Stus[0] = ' YBQ '
Print (Stus)

#查
Print (Stus)
Print (Stus[1])
Print (Stus.count (' YBQ ')) #查看某个元素的个数, if the element does not exist, returns 0
Print (Stus.index (' Xiaohei ')) #找到某个元素的下标, if there are multiple, return the first, if the element does not exist, it will be an error

#删
Stus.pop (1) #默认删除最后一个元素, if you specify subscript, delete the specified element
Print (Stus.pop (1)) #打印 deleted values
Print (Stus)
Stus.remove (' Xiaohei ') #直接写元素, if there are multiple elements, delete only one
Print (Stus)
Del Stus[1] #删除指定下标的值
Stus.clear () #清空整个list

#反转list
Stus.reverse ()
Print (Stus)
#
#排序, the default sort is ascending
Stus.sort ()
Stus.sort (reverse=true) #指定reverse =true, which is descending order
Print (Stus)

#多维数组
#二维 three-dimensional four ...
All_num = [123,456,[789,10,11]]
three = All_num = [123,456,[789,10,11,[12,13]]
Print (all_num[2][1]) #先找外边 look inside.
#
All_num.extend (three) #把两个list合并到一起
Print (All_num)

List loops and slices

 mun = [1,2,3,4,5,6,7,8,9,10] 
 Print (Mun[1:6:2]) #步长 2 means to take a 
 print (mun[-1:-6:-2]) #步长是正数的从左往右取 every two, if it's a negative number , from right to left, the preceding value must also write negative 
 #切片同样适用于字符串, the string also has subscript 
 title = ' Send red envelopes today ' #空格也算一个字符串 
 Print (title[1]) 
 Print (Title[1:3]) 
 for T,h in enumerate (title): #enumerate可以同时循环下标和值 
 Print ('%s:%s '% (t,h)) #同时打印下标和值 
 
 2. Dictionary Operation 

 #字典是key-vlue form of 
 D = {
 ' name ': ' YBQ ', 
 ' age ': ' + ', 
 ' addr ': ' Haidian ' 
} 
 #特点: Value convenience fast 
 pri NT (d[' name ']) #如果写了不存在的值, error 
 Print (d.get (' ag0e ')) #如果写了不存在的值, return none, 
 Print (D.get (' ag0e ', ' dou ') #如果写了不存在的值 , after the value is written, it returns the written value Dou, 
 # 
 #字典是无序的 
 #增 
 d[' Shengao ']=198 
 D.setdefault (' Tizhong ', *) 
 # 
 #改 
 D [' Shengao ']=198 
 D.setdefault (' Tizhong ', ') #这种方法不能修改值, only new 
 # 
 #删除 
 D.pop (' Shengao ') 
 Print (d) 
 D.popitem () #随机删除一个数值, no use, basically less than 
 del d[' Shengao ' 
 # 
 D.clear () #清空字典 
 
 #获取所有key和value 
 Print (     D.keys ()) 
 Print (D.values ()) 
 # 
 # 
 If ' mane ' in D: #判断字典中是否有此值 
 Pass 
 
 #字典循环 
 for i in D: 
 Print (i) 
 for k,v in D.items (): 
 Print (k,v) 
 Print (D.items ()) 
 for K in D: #性能最好 
 Print (K,d[k] 
 
 #强制类型转换 
 Int () 
 Str () 
 List () cast to list using 
 Res = list (D.items ()) 
 Print (res[0]) 
 
 3. Tuple operations 

Print (Type (a)) #查看是什么类型
b= (1,2,3,4,5)
#元祖也是一个list, just immutable, unable to modify
B.count (1)   #找个数
B.index (1)   #返回下标

4. File read and write operations

f = open (' Read and write Records '. txt ', ' A + ', encoding = ' utf-8 ')
F.seek (0) #seek移动指针的时候, only to read so, not to write well
Print (F.read ()) #读取文件里的全部内容
Print (F.readline ()) #只读一行内容
Print (F.readlines ()) #读取文件里的全部内容, put the contents of the file into a list
name = [' Ybq ', ' YB ']
F.write (name) #只能传字符串
F.writelines (name) #写的时候传入一个可迭代的对象即可, is a recyclable
F.truncate () #清空文件内容
F.tell () #查看当前指针位置
F.write (' ybq ' + ' \ n ')
#循环
For I in F:
   Print (i)
F.close ()

#flie ()   Python2 inside the method
#文件打开有三种方式, if the mode is not specified when opening, the default is read
# Read R
#  r+    Read and write mode, as long as the R, the file does not exist when the Open will be error
# write W       this mode will empty the original file contents
# w+   write mode, as long as the W, the contents of the file will be emptied
#追加 A
#追加读写 A +

5. String methods

#可变变量 List Dictionary
#不可变变量 progenitor, String value cannot be modified

Li = [1,1,2,3,4,5,6,7,8,9]
Li2 = li[:] #深拷贝
Li2 = li# Shallow copy
For I in Li:
If i%2!=0:
Li.remove (i)
Print (LI)
#在循环list的时候不能删东西, this will cause the subscript to change and a copy can be resolved.
#
ID (LI) #查看内存地址
Print (ID (LI))
Print (ID (li2))

#字符串方法都不会改变原来的值
Name = ' Besttest rich '
Print (name)
Print (Name.strip ()) #默认去掉两边的空格和换行符
Print (Name.strip (' besttest '))
Print (Name.lstrip ()) #去掉左边的空格和换行符
Print (Name.rstrip ()) #去掉右边的空格和换行符
Print (Name.count (' t ')) #查找某个字符在字符串里的个数
Print (Name.upper ()) #把所有的大写字母都变成小写
Print (Name.lower ()) #把所有的小写字母都变成大写
#
NA = ' select * from '
Print (Name.startswith (' select ')) #判断字符串是以XX开始的
#
na = ' 1.jpg '
Print (Name.endswith ('. jpg ')) #判断字符串是以XX结尾的
#
f = ' {name} welcome '
Print (F.format (name= ' YBQ ')) #格式化
#
f = ' {name} welcome '
D = {' name ': ' YBQ '}
Print (F.format_map (d)) #字典形式格式化
#
Print (Name.replace (' t ', ' d ')) #字符串替换, the first one is old, the second is the new one.
Print (Name.isdigit ()) #是否是数字
Print (' 123 '. IsDigit ()) #是否是数字
#
Print (Name.isalnum ()) #是否包含数字或字母
Print (Name.isalpha ()) #是否是英文字母
#
Print (Name.capitalize ()) #首字符大写
Print (Name.center, ' * ') #字符串放中间, both sides are padded with *
Print (Name.find (' t ')) #找到这个字符, and returns the subscript, if not present-1
Print (Name.index (' t ')) #找到这个字符, and returns the subscript, if not present, an error

st = ' a,b,c,d,e,f,g '
St_list=st.split (', ') #以逗号分隔字符串, write nothing, separate by space
Print (st_list)

Slist =[' A ', ' B ', ' C ']
SD = ', '. Join (slist) #以逗号连接字符串
Print (SD)

Automated DAY3---python basics (list, dictionaries, tuples, file read and write, string formatting)