Python: File operations

Python: File operations

Open () calls the built-in functions, built-in function calls within the system's internal open, all operations on the file are based on the file handle F1.

Steps for file operations:

Close file, open file, action file

Remember: Finally close the file (otherwise there may be unexpected results)

Open File

File handle = open (' File path ', encoding= ' Specify file Encoding ', mode= ' mode ')

F1 = Open (r'd:/Contact form. txt', encoding='GBK', mode='R') #指定绝对路径Print(F1.read ()) F1.close () F1= Open ('Log1', encoding='GBK', mode='R') #相对路径是在该py文件同级目录下Print(F1.read ()) F1.close ()

To prevent forgetting to close a file, you can use the context Manager to open the file

With open (' File path ', ' mode ') as file handle:

With open ('Log1', encoding='Utf-8') as F1, open ('log2', encoding='Utf-8', mode='W') as F2:content=F1.read () f2.write (content) with open ('Log1', encoding='Utf-8') as F1:Print(F1.read ()) F1.close ()PassWith Open ('Log1', encoding='Utf-8', mode='W') as F2:f2.write ('666')

The mode of opening the file is:

R, read-only mode (default). W, write-only mode. "Non-readable; does not exist; create; Delete content;" A, append mode. "readable; not present; create; append only;" R+, can read and write files. "readable, Writable, append" W +, write "U" means that when reading, \ r \ n \ r \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ r \ r+ mode is used RUr+ U " b " represents the processing of binary files (such as: FTP send upload ISO image file, Linux can be ignored, Windows processing binary files need to be labeled) Rbwbab

Close File

File handle. Close ()

File: Read

#读 R
#1 Read () All outF1 = open ('Log1', encoding='Utf-8') Content=F1.read ()Print(content) F1.close ()#2 read (n) reading partF1 = open ('Log1', encoding='Utf-8') Content= F1.read (3)Print(content) F1.close () F1= Open ('Log1', mode='RB')Print(F1.read (3). Decode ('Utf-8') ) F1.close ()#R-Mode read (n) n reads by character. #RB mode read (n) n reads in bytes. #3 ReadLine () read by lineF1 = open ('Log1', encoding='Utf-8')Print(F1.readline ())Print(F1.readline ())Print(F1.readline ()) F1.close ()#4 readlines () reads each line sequentially F1 = open ('Log1', encoding='Utf-8')Print(F1.readlines ()) F1.close ()#5 for LoopF1 = open ('Log1', encoding='Utf-8') forLineinchF1:Print(line) f1.close ()

# r+  Read -Write F1 = open ('log1', encoding='utf-8', Mode='r+')print(F1.read ())f1.write (' 666 ') f1.write ('a')print(F1.read ()) F1.close () 

File: Write

#w No files, new file write content#with the original file, the content is first emptied, and the new content is written. F1 = open ('log2', encoding='Utf-8', mode='W') F1.write ('Peach in vain FDKSAGDFSA') F1.close ()#Reading and writing of imagesF1 = open ('1.jpg', mode='RB') Content=f1.read () F2= Open ('2.jpg', mode='WB') f2.write (content) F1.close () f2.close ()#w+ First Write and then readF1 = open ('log2', encoding='Utf-8', mode='w+') F1.write ('two engines.') F1.seek (0)Print(F1.read ()) F1.close ()#Append a#a no file, new file write contentF1 = open ('Log3', encoding='Utf-8', mode='a')#F1.write (' Alex 666 ')F1.write ('\nalex 666') F1.close ()#A +F1 = open ('Log3', encoding='Utf-8', mode='A +') F1.write ('Python22 Period') F1.seek (0)Print(F1.read ()) F1.close ()

Files: changing

The procedure is as follows:

# 1, open the original file in read mode.
# 2, open a new file in write mode.
# 3, read the original file as required modify to write the modified content to the new file.
# 4, delete the original file.
# 5, rename the new file to the original file.

ImportOswith Open ('file', encoding='Utf-8') as F1, open ('File.bak', encoding='Utf-8', mode='W') as F2:old_content=f1.read () new_content= Old_content.replace ('Alex','SB') F2.write (new_content) os.remove ('file') Os.rename ('File.bak','file')

Upgrade version

ImportOswith Open ('file', encoding='Utf-8') as F1, open ('File.bak', encoding='Utf-8', mode='W') as F2: forLineinchF1:new_line= Line.replace ('SB','Alex') F2.write (new_line) os.remove ('file') Os.rename ('File.bak','file')

Other operations:

#whether the readable is readable#whether writable can be written#F1.seek (#任意调整)#F1.seek (0,2) #光标调整到最后#f1.seek (0) #光标调整到开头#F1.tell () #告诉光标的位置#f1.truncate (3) #按照字节对原文件进行截取 must be in a or a + modeF1= Open ('Log3', encoding='Utf-8', mode='A +')#f1.write (' python22 period ')#print (F1.read ())Print(F1.readable ())Print(F1.writable ()) F1.close () F1= Open ('log2', encoding='Utf-8') F1.read ()Print(F1.tell ())Print(F1.seek (0))Print(F1.seek (0,2)) F1.seek (02H#arbitrary AdjustmentF1.seek (0,2)#the cursor adjusts to the lastF1.seek (0)#the cursor adjusts to the beginningPrint(F1.tell ())#tell the cursor wheref1.close () F1= Open ('Log3', encoding='Utf-8', mode='A +') F1.truncate (3)#interception of the original file according to Byte must be in a or a + modeF1.close ()

Python: File operations