Draft python (list, dictionary, tuple, string method, file read and write)

1. List

Define List

A = []

adding elements

A.append (' xx ') #在list末尾添加

A.insert (0, ' abc ') #在指定某位置添加元素, the specified subscript does not exist and is added at the end

modifying elements

A[0] = ' BB ' #找到元素下标, re-assigned

View

Print (a)

Print (A[0])

A.count (' abc ') #查看元素在list里的个数, does not exist return 0

A.index (' abc ') #查元素下标, repeat multiple, show first, do not exist then an error

Delete Element

A.pop () #默认删除最后一个元素, the value of the deleted element is returned, or the subscript is specified, the subscript is deleted, the error does not exist

A.remove (' xx ') #删除list里元素, if there are multiple, delete only one

Del A[0]

A.clear () #清空整个list

Slice

A[0:3]

#顾头不顾尾, the last one will not be evaluated

#[0:] [: 3] [:: 1] Step

It doesn't matter.

A.reverse () #反转list顺序

A.sort () #排序, default ascending, specified Reverse=true descending

Multidimensional arrays

A = [A]

b = [4,5,6]

A.extend (b) #合并两个list

2. Dictionaries

Dictionaries are unordered.

Defining dictionaries

A = {}

Check

A = {' BB ': ' CC '}

A.get (' BB ') #get不到, return None

Increase

a[' dd '] = ' ee '

A.setdefault (' ff ', ' GG ')

Modify

a[' dd '] = #key存在, re-assigned

By deleting

A.pop (' DD ') #因为字典是无序的, must pass key

A.popitem () #默认随机删除一个

del a[' BB ']

A.clear () #清空字典

3. String method

For i,t in Numerate (a): #可以同时循环下标和值

", strip () #去空格和换行符

", Split () #分割字符串

", Upper () #变成大写

", Lower () #变成小写

", Count (' AA ') #出现的次数

', '. Join () #把list变成字符串并且以, split

". EndsWith #判断以什么什么结尾, return to True,f

". StartsWith #判断以什么什么开头

". IsDigit () #判断是不是纯数字

4. File reading and writing

Open it

f = open (' xx ') #默认只读模式打开

R Read-only r+ read and write, file does not exist will error

W Write w+ Read and write, will empty the file

A + read and write, the file pointer by default at the end

F.seek (0) #移动指针到最前面, a + open need to use this

F.read () #读取文件里所有内容, returns a string, reads the pointer at the end

F.readline () #只读一行内容, return string

F.readlines () #读取文件里所有内容, returns list,list each element is a row of data

F.write (' AA ') #只能写字符串

F.writeslines () #写可迭代对象

F.tell () # Gets the position of the current file pointer

F.close #关闭文件

Draft python (list, dictionary, tuple, string method, file read and write)