Python3 file read and write operations

How do I read and write files in python?
Four parts:
Open File
Read file

Write file
Close File

Example:
How to open children files and show

Data=open ('children') #指向要打开的文件f=data.read () #读取文件内容 and assigned to Fprint (f) # Print file Data.close () #关闭文件, equivalent to returning memory

File open default is read-only permission, but we can open the file with additional permissions, such as Read and write

Data=open ('children','r+', encoding='utf-8  ') F=data.read ()print(f)print# View data Whether this file is readable Print (Data.writable ())  # View data whether this file is writable

Data.close ()

Operation Result:

Hello Word

True

True

Read the contents of a file row by line

Use for loop to read

Data=open ('children','r', encoding='utf-8  ') for in range (1,5):    f=data.readline ()     Print (" prints line%d:" %i,f)

Operation Result:
Print line 1th: My name is children

Print Line 2nd: come from Beihai

Print line 3rd: like Bie

Print Line 4th: chenchaozhen

If you don't use a for loop, you can write only one line.

Data=open ('Children','R', encoding='Utf-8') F=Data.readline ()Print("First line", f) F=Data.readline ()Print("Second Line", f) F=Data.readline ()Print("Third line", f) F=Data.readline ()Print("Line Fourth", f) F=Data.readline ()Print("Line Fifth", F) data.close ()

Operation Result:
Print line 1th: My name is children

Print Line 2nd: come from Beihai

Print line 3rd: like Bie

Print Line 4th: Chen

Note that ReadLine reads a row, while ReadLines reads all and saves it as a list

Data=open ('children','r', encoding='utf-8  ')print#readlines is read all rows into a list form

Operation Result:

[' 1\n ', ' 2\n ', ' 2\n ', ' 3\n ', ' 4\n ', ' 5\n ']

Why would there be a \ n?

Because the Windows platform line break is \ n

How do I write the specified content to a file?

When the open file is given W permissions

Data=open ('children','w', encoding='utf-8  '# write mode data.write ("11112222"# Data.close ()

# #注意w权限是重新创建一个同名文件, then overwrite the source file

# #其实文件的修改可以理解为覆盖, overwrite old content with new content

Like ReadLines, Writelines is the same, but one is to read one is to write

Data=open ('Children','W', encoding='Utf-8') Data.writelines ("11112222\n")#Line-wise writeData.writelines ("11112222\n")#does not overwrite the previous line, which is equivalent to list writingData.writelines ("1223123") Data.close ()

You can also write this:

Data=open ('children','w', encoding='utf-8  ') data.writelines (['Chen Chao zhen \ n','  Xu Zhen zhi \ n'# So if you want to write more than a row, you can write it as a list data.close ()

#但是要注意, the list is inserted in the form of the last to add a \ n

#追加模式, the source file is not emptied and the content is appended to the last file

Data=open ('children','a', encoding='utf-8  '# Append mode data.writelines (['Chen Chao zhen \ n', ' Xu Zhen zhi \ n ' ]) data.close ()

The file has not been modified so that only covers
R Read mode
W Write mode (re-create an empty file with the same name)
A append mode (the Write content is appended to the last line of the file)
r+ Read-write mode (writes are overwritten from the beginning of the file, not empty files with the same name)
w+ Read-write mode (re-create an empty file with the same name)
A + append read and write mode (same as a mode)

1. Document A.txt content: Each line content is the product name, the price, the number, to find out the total amount of money spent on this shopping

Apple 10 3
Tesla 100000 1
MAC 3000 2
Lenovo 30000 3
Chicken 10 3

In the file open there is also a keyword with

With open ('children','r+') as name:    Print (Name.readlines ())

Open file and create variable to point to file, can be completed in one step

With open ("a.txt",'r') as much:    res=[]    res1=[]    for in  much:        res.append (line)       for in range (0,5):        a=int (Res[i].split () [1])        b=int (Res[i].split ( ) [2])        res1.append (a*b)    print(sum (res1))

Operation Result:
196040

Python3 file read and write operations