DAY-08 file operation

f.close()

f = open ('source.txt' , 'r', encoding='utf-8' ) f.read() # Read all content at once

f.read(10) # read the specified number of characters

f.readline() # read one line at a time The basis of this reading)

f.readlines() # read and save all the content, and press the line feed mark as the read One-time basis, stored as a list

f.close()

wf = open('target.txt', 'w', encoding=< span style="color: #800000;">'utf-8' span>) wf.write('123
') # Write one at a time, the line must be marked with 


wf.write('456
') wf.flush() #  Send a message to the operating system to refresh the data written in the memory to the hard disk

wf.write('789
') wf.writelines([' abc
', ' def
', 'xyz
']) # Write multiple lines at once, the lines must be marked with 


 wf.close() # 1. Refresh the data written in the memory to the hard disk 2. Free up hard disk space

< span style="font-size: 14pt;">part1 # as alias, rf holds variable of file resource

with open('target.txt', 'r', encoding='utf-8') as rf:  # Specific code for file operations # Once the indentation is cancelled, the resource is released

 part2 with open('target.txt', 'r', encoding='utf-8') as rf1, open('target1.txt', 'r', encoding='utf-8') as rf2: print span>(rf1.read()) print(rf2.read()) # print(rf1.read( )) # Report an error # print(rf2.read()) # Report an error

 part3 with open('target.txt ', 'r', encoding='utf-8') as rf1: with open( span>'target1.txt ', 'r', encoding='utf-8') as rf2:  print( rf1.read()) print(rf2.read())  # print(rf1.read()) # Can be operated

 # print(rf2.read()) # Cannot operate< /span>

with open('target.txt', 'r', encoding='utf-8') as rf: with open('target2.txt', 'w< /span>', encoding='utf-8') as wf: for line in rf: wf.write(line ) with open('target.txt', 'rb') as rf: with open( 'target3.txt', 'wb') as wf: for line in rf: wf.write(line)

with open('001.mp4', 'rb') as rf: with open('002.mp4', 'wb') as wf: for line < span style="color: #0000ff;">in rf: wf.write(line)

Cursor operation

1. The cursor operates on bytes, so it can only be operated in b mode
2. Cursor Operation can change the operating position. In r mode, you can change the position to operate. All main modes select r mode
3.seek(offset, whence):
　　—offset is an integer, which means the number of bytes to shift backwards, and a negative number means how many bytes to shift forwards< br>　- whence: 0 means set the cursor to the beginning, 1 means from the current position, 2 means set the cursor to the end

# You are Japanese

with open('target.txt', 'rb') as f: #< span style="color: #008000;"> read 6 bytes first

 data = f.read(6) print(data.decode( 'utf-8'< /span>)) # You are

 # Offset the cursor by 3 bytes from the beginning

 f.seek(3, 0) data = f.read(6) print(data.decode('utf-8')) # It’s the day

 # offset 3 bytes from the current cursor position

 f.seek(-3, 1) data = f.read(3) < /span>print(data.decode('utf-8')) # Day

 f.seek(-3, 2) data = f.read (3) print(data.decode('utf-8')) # People

< pre>print(u‘abc‘) #< /span> For display

print(b'abc') # Used to pass 

print< /span>(u'a	b
c') print(r'a	b
c') # Unescaping

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

data = f.read()

f.close()

f = open('< span style="color: #800000;">source.txt', '< /span>r', encoding='utf-8') f.read() # read all content at once End

f.read(10) # read the specified number of characters

f.readline() # read one line at a time The basis of this reading)

f.readlines() # read and save all the content, and press the line feed mark as the read One-time basis, stored as a list

f.close()

wf = open('target.txt', 'w', encoding='utf-8 ') wf.write('123
') # Write one at a time, the line must be marked with 


wf.write('456
') wf.flush() #  Send a message to the operating system to refresh the data written in the memory to the hard disk

wf.write('789
') wf.writelines([' abc
', ' def
', 'xyz
']) # Write multiple lines at once, the lines must be marked with 


 wf.close() # 1. Refresh the data written in the memory to the hard disk 2. Free up hard disk space

part1 # as is an alias, rf holds variables for file resources

with open('target.txt', 'r', encoding='utf-8') as rf:  # Specific code for file operations # Once the indentation is cancelled, the resource is released

  part2 with open('target .txt', 'r', encoding='utf-8') as rf1, open('target1.txt', 'r', encoding='utf-8 ') as rf2: print(rf1.read()) print(rf2.read() ) # print(rf1.read()) # report an error # print(rf2.read()) # Report an error

< /p>

 part3 with open(< /span>'target.txt', 'r', encoding='utf-8') as rf1: with open(' target1.txt', 'r', encoding='utf-8') as rf2: print(rf1.read()) print(rf2.read()) #< span style="color: #008000;"> print(rf1.read()) # Can be operated

 # print(rf2.read()) # Cannot operate< /span>

# rt: The file must exist in advance, there is no error, the file operation is in the form of characters-abbreviated as r #  wt: The file can exist or not exist. If it exists, it will be cleared and written. If it does not exist, it will be written after creation. File operations are in character form-abbreviated as w  # at: The file can exist or not, and the existing content is appended to the end of the previous content. Write after creation does not exist, file operations are in character form-abbreviated as a



# rb: The file must exist in advance, there is no error, the file operation is in byte format  # wb: The file can exist or not, if it exists, it will be cleared and written , There is no write after new creation, file operations are in byte format # ab: file It can exist or not. There is additional writing at the end of the previous content, and there is no writing after new creation. File operations are in byte form.



# r+t: The file must be readable and writable, and replace it from the beginning by default Write, operate by character # w+t: The file exists, clears, but does not exist, can be created Read and write, operate by character # a+t: file exists, append does not exist, create Readable and writable, operated by characters



# r+b: The file must be readable and writable, and replace it from the beginning by default Write, operate by byte # w+b: File exists, empty, but not created Read and write, operate in bytes There are created readable and writable, byte operations

with open( 'target.txt'< /span>, 'r ', encoding='utf-8') as rf: with open('target2.txt',  'w‘, encoding=‘utf-8‘) as wf: for line in rf: wf.write(line) with open(‘target.txt‘, ‘rb‘) as rf: with open(‘target3.txt‘, ‘wb‘) as wf: for line in rf: wf.write(line)

with open(‘001.mp4‘, ‘rb‘) as rf: with open(‘002.mp4‘, ‘wb‘) as wf: for line in rf: wf.write(line)

# 你是日本人

with open(‘target.txt‘, ‘rb‘) as f: # 先读6个字节

    data = f.read(6) print(data.decode(‘utf-8‘))  # 你是

    # 将游标从头开始往后偏移3个字节

    f.seek(3, 0) data = f.read(6) print(data.decode(‘utf-8‘))  # 是日

    # 从当前游标位置往前偏移3个字节

    f.seek(-3, 1) data = f.read(3) print(data.decode(‘utf-8‘))  # 日

 f.seek(-3, 2) data = f.read(3) print(data.decode(‘utf-8‘))  # 人