Joson wrote:
Hi all,
Now I have a text file about 1MB. Sometimes I need to remove the
last line.
The current method I use is reading all content, finding the last
sentence, remove it and write the new content to the file.
So, it need to read a 1MB file and write a 1MB file. It's
ineffictient, I think. Are there any other methods?
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Take a look at file.seek to move to a specific section of the file and
file.truncate to truncate a file at a specific size, rough
implementation would be something like.
BUFFER = 2**10 # Set your buffer size
f = open(filename, 'r')
multiple = -1
found_it = False
while not found_it:
f.seek(BUFFER * multiple, os.SEEK_END)
# Seeks from the file endpoint the specified by your buffer *
'iteration' of the app
offset = f.tell() # gets the current position
data = f.read(BUFFER) # read in your data and process it
# perform operations to get your termination point offset
if termination_point_not_found:
multiple -= 1
else:
# once you find your position to end the file on truncate the
file and exit loop
f.truncate(offset + termination_point_offset)
found_it = True
f.close()
It's untested code, but it should work just fine.
As for how fast it is by comparison, I unfortunately don't have time to
benchmark it.
--
Kind Regards,
Christian Witts
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