python-file operations

1. File opening

Open mode:

f = open('test.txt','r')

#r, read-only mode, when the file does not exist, an error will be reported

f = open('test. txt','w')

#w, write-only mode, create the file when the file does not exist, clear the original file when the file exists

f = open('test.txt','x')

# x, a new mode in python3. When the file exists, an error will be reported. When the file does not exist, create the file and write

f = open('test.txt','a')

#a, append mode, the file will not When it exists, create the file

Encoding format:

The above opening mode, the default encoding='utf-8', when garbled characters appear when opening the file, it may be caused by inconsistent encoding formats

At this time, you can adjust the encoding Format to read files

f=open('test.txt','r',encoding='utf-8')

f=open('test.txt','r',encoding='gbk' )

bytes mode:

When the b parameter is used, the file will be opened in byte mode. When the b parameter is not applicable, the file will be opened in character mode

f=open('test.txt','wb' )
f.write(b'xe7xbbxbfxe8x8cxb6')
f.close()
=>Write test.txt in byte mode
n = open('test.txt','r',encoding='utf- 8')
t = n.read()
print (t)

=> There is no b parameter, the file is read in character mode, and it is displayed as green tea

2. File operation

f=open(' test.txt','r',encoding='utf-8')

f.seek()

=>Move the current pointer position to the specified position. When the mode is opened and there is no b parameter, it is as follows Character position movement, when opened with the b parameter, moves the pointer according to the byte position

f.tell()

=> Gets the byte position of the current pointer, regardless of the opening mode

f.flush()

=>Strong brushing. Generally, when writing or modifying a file, it is cached first, and then written to the file when the file is closed. When using this function, the modified content is directly written to the file

f.fileno

=>File descriptor

f.truncate()

=>Truncate all content after the current pointer position

3. File close

Method 1:

f=open('test.txt ','r',encoding='utf-8')

n = f.read()

f.close()

Method 2:

with open('test.txt','r', encoding='utf-8') as f:

n =f.read()

When using with, the close operation of the file will be automatically performed

And, using with, you can open 2 files at the same time:

with open ('test1.txt','r',encoding='utf-8') as f, open('test2.txt','w',encoding='utf-8') as h:

data = f .read()

h.write(data)