truncate()

truncate(limit)
limit : (optional) upper limit of resizing the file.
If limit is not given the the truncate() works from the current position of file object.

Using mode 'a'

fob=open('data.txt','a')
fob.truncate()
fob.close()
# read the file
fob=open('data.txt','r')
print(fob.read())
Output is here ( used the data.txt file given at file read() )
This is first line
This is second line
This is thrird line
This is fourth line
In the above code we have not used limit so in mode = 'a' file pointer remains at the end of the file. So no data is truncated.

Using limit

fob=open('data.txt','a')
fob.truncate(13)
fob.close()
# read the file
fob=open('data.txt','r')
print(fob.read()) # This is first

using mode 'r'

We can't use mode 'r', this will generate error message.

using mode 'w'

When mode is ‘w’ file pointer remains at the beginning of the file to overwrite the content, hence there is no difference in using truncate() in this mode.
fob=open('data.txt','w')
fob.truncate(10)
fob.close()
# read the file
fob=open('data.txt','r')
print(fob.read())
writable()

File Append File Write


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