CODEWITHSUNDEEP
python-3.xfilefile-writing
Mathew
Mathew

Reputation: 1430

python3 os write, end file

I have am trying to open a file for writing and I am using os.write() because I need to lock my files. I don't know how to write a string to the file and have the remaining file content removed. For example, the code below first writes qwertyui to the file, and then writes asdf to the file, which results in the file containing asdftyui. I would like to know how I can do this so that the resulting content of the file is asdf.

import os

fileName = 'file.txt'

def write(newContent):
    fd = os.open(fileName,os.O_WRONLY|os.O_EXLOCK)
    os.write(fd,str.encode(newContent))
    os.close(fd)

write('qwertyui')
write('asdf')

Upvotes: 0

Views: 755

Answers (2)

PX374
PX374

Reputation: 31

import os

fileName = 'file.txt'

def write(newContent):
    fd = os.open(fileName,os.O_WRONLY|os.O_EXLOCK)
    Lastvalue = os.read(fd, os.path.getsize(fd))
    os.write(fd,str.encode(Lastvalue.decode() +newContent))
    os.close(fd)

write('qwertyui')
write('asdf')

Upvotes: 1

DYZ
DYZ

Reputation: 57033

Add os.O_TRUNC to the flags:

os.open(fileName,os.O_WRONLY|os.O_EXLOCK|os.O_TRUNC)

Upvotes: 1

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