Fourth day of basic Python learning

4.1 Encoding and decoding

4.2 File operations

8th Day of self-study, title arranging study fourth day

Encode encoding

Docode Decoding

Python2 default ASCII format

#-*-Coding:utf-8-*-# What is the code format for declaring a program

# decode text into Unicode format

sname = Name.decode ("Utf-8") # must first declare what the decoded format is, such as Utf-8print (sname) ssname = Sname.encode ("GBK") # encode text into GBK format print (ssname)

# It must be noted that when GBK turns into Utf-8, it must first be converted to Unicode and then to Uft-8, and vice versa.

Python3 default Unicode

b = byte = byte type = 2 binary

Py3 and Py2 Coding differences

Encode the data into the bytes type while coding

Decode the bytes type into a string while decoding

The method that can be called must be an object

File operations, the following methods are used in the file Operation object

R: Read mode operation

W: Write Action Object

A: Append add

r+: Read- write mode when you use write, the text is appended to the end of the last line

w+: Write mode when you use write, the contents of the file are emptied before being written to the file

A +: Additional Reading

Open (1)# on, 1 means one character is printed only

Close# closing files

Write# writing mode

RA = open (' Test file ', ' W ', encoding= ' utf-8 ')

Ra.write ("is the first line to test the string.")

Print (RA)

Ra.close ()

Print Result: <_io. Textiowrapper name= ' test file ' mode= ' W ' encoding= ' Utf-8 ' >

RA = open (' Test file ', ' R ', encoding= ' utf-8 ')

rar = Ra.read ()

Print (RAR)

Ra.close ()

Print Result: Is the first line to test the string.

RAA = open (' Test file ', ' a ', encoding= ' utf-8 ')

Raa.write (' is the second line test string ')

Raa.close ()

Hit this text result: is the first line to test the string. That's the second line. The test string is not wrapped by default, and the default insertion is at the cursor

RAA = open (' Test file ', ' a ', encoding= ' utf-8 ')

Raas = Raa.write (' \ n is the second line test string \ n ')

Raa.close ()

Unlike the previous one, it wraps after the line break

File Operation Flow:

1, open the file, get the file handle and assign value to a variable;

Handle: The Action object of the file

2, through the handle to the file operation;

3. Close the file

ReadLine () Print line default first row

ReadLines () Print all Lines

# Open a test file in a read-only manner, formatted as Utf-8file = open (' Test file ', ' R ', encoding= ' Utf-8 ') # Assign a file variable a = File.readlines () # set an initial value nubmer=0# Loop to print the value of the A-file variable, starting with the first for I in a:# initial value every time you add 1 to 2, use join to change the configuration item to this line, do not print the/n newline character nubmer+=1 if Nubmer = = 2:i = ". Join ([ I.strip (), ' AAAAA ') # Every time this line is printed, when the 2nd time equals join then output the value of the 2nd time variable print (I.strip ()) # Close the file Operation properties, A.close ()

Modify a file

# define two variables and files

F_read = open (' Test file ', ' R ', encoding= ' utf-8 ')

F_write = open (' Test file 2 ', ' W ', encoding= ' utf-8 ')

Number = 0# Sets the variable to 0 loops for a file line, each time adding 1for f in F_read:number + = 1 if numbers = = 2:# When 2 o'clock, assign a f= ' Xiong test to the file variable string. \ n ' F_write.write (f) # finally write it to a new file, you can complete the change file operation

# to manage a single object, this method no longer needs to use the close () method

With open (' Test file ', ' R ', encoding= ' utf-8 ') as F1:

Pass

# Manage Multiple objects

With open (' Test file ', ' R ', encoding= ' Utf-8 ') as F1,open (' Test file 2 ', ' W ', encoding= ' Utf-8 ') as F2:

Pass

Tell detect cursor Position

Print (File.read (4))

Print (File.tell ())

Print Result: is the first

3 characters in Chinese, uft8 format

The file object. Seek () adjust the cursor position

Print (File.seek (1))

Print (File.tell ())

Printed results: 1

1

Flush: Data is removed from the cache and stored synchronously with the disk

Import Sys,time

Sys.stdout.write ("*")

# truncation is done in write mode, must use Write,append format

Truncate # empty file contents

Fileno# File descriptor

Isatty# to see if it's an end device

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Fourth day of basic Python learning