Python Notes-----file operations

File operations

Create a file with the name filename

Content is

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Print file Encoding

f = open ("filename", ' R ', encoding= "Utf-8")
Print (f.encoding)

Utf-8

Number of printed in memory

Print(F.fileno ())

3

1. File read Operation 1.1 open () method, mode default read

f = open ("filename", encoding= "Utf-8")
data = F.read ()
Print (data)

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1.2 Read the first few lines

f = open ("filename", encoding= "Utf-8")
For I in range (2):
Print (F.readline (). Strip ())

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1.3 lines are finished reading

f = open ("filename", encoding= "Utf-8")
For I in F:
Print (I.strip ())

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1.4 Efficient reading to line X

Count = 0
f = open ("filename", encoding= "Utf-8")
For I in F:
if Count = = 3:
Print ('----------------')
Count + = 1
Print (I.strip ())
Count + = 1

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----------------
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Ssssss

2. File write operation 2.1 W write mode, if no this file is created

f = open ("Filename2", ' W ', encoding= "Utf-8")
F.write ("Wwwww")
F.close ()
F1 = open ("filename2", encoding= "Utf-8")
data = F1.read ()
Print (data)
F.close ()

Wwwww

2.2 A Append mode

Append at end of file

f = open ("filename", ' a ', encoding= "Utf-8")
F.write ("\nssssss")
F.close ()

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Ssssss

2.3 Read + Append mode

f = open ("FileName", "r+", encoding= "Utf-8")
F.write ("\ n------haha------------")

For I in F:
Print (I.strip ())

2.4 File Modification

f = open ("FileName", "R", encoding= "Utf-8")
F1 = open ("Filename1", "W", encoding= "Utf-8")

For line in F:
If "H" in line:
line = line. Replace (' H ', ' G ')
F1.write (line)
F.close ()
F1.close ()

3. Pointer operation

f = open ("filename", encoding= "Utf-8")
Print (F.tell ()) #查看当前指针位置
Print (F.readline ())
Print (F.tell ())
F.seek (0) #指针回到0
Print (F.tell ())
Print (F.readline ())
Print (F.tell ())

0
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4
0
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4

4. Determine if the file can be read and writable

f = open ("filename", ' R ', encoding= "Utf-8")

Print (F.readable ())
Print (F.seekable ())
Print (F.writable ())

True
True
False

5.flush method and Buffer method

f = open ("filename", ' R ', encoding= "Utf-8")
Print (F.flush ()) #从内存写入磁盘
Print (F.buffer)

None
<_io. BufferedReader name= ' filename ' >

6. Implement the progress bar

Import Sys,time

For I in range (10):
Sys.stdout.write ("#")
Sys.stdout.flush ()
Time.sleep (0.5)

##########

7. Truncation

f = open ("FileName", "a", encoding= "Utf-8")
F.seek (0) #指定指针到0的位置

F.write ("123456")

F.truncate (2) #截断2字符

Only 2 characters are reserved in the filename file

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Python Notes-----file operations