How to delete only the content of file in python

Question

I have a temporary file with some content and a python script generating some output to this file. I want this to repeat N times, so I need to reuse that file (actually array of files). I'm deleting the whole content, so the temp file will be empty in the next cycle. For deleting content I use this code:

def deleteContent(pfile):      pfile.seek(0)     pfile.truncate()     pfile.seek(0) # I believe this seek is redundant      return pfile  tempFile=deleteContent(tempFile) 

My question is: Is there any other (better, shorter or safer) way to delete the whole content without actually deleting the temp file from disk?

Something like tempFile.truncateAll()?

Answer 1

How to delete only the content of file in python

There are several ways of setting the logical size of a file to 0, depending how you access that file:

To empty an open file:

def deleteContent(pfile):     pfile.seek(0)     pfile.truncate() 

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To empty an open file whose file descriptor is known:

def deleteContent(fd):     os.ftruncate(fd, 0)     os.lseek(fd, 0, os.SEEK_SET) 

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To empty a closed file (whose name is known)

def deleteContent(fName):     with open(fName, "w"):         pass 

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I have a temporary file with some content [...] I need to reuse that file

That being said, in the general case it is probably not efficient nor desirable to reuse a temporary file. Unless you have very specific needs, you should think about using tempfile.TemporaryFile and a context manager to almost transparently create/use/delete your temporary files:

import tempfile  with tempfile.TemporaryFile() as temp:      # do whatever you want with `temp`  # <- `tempfile` guarantees the file being both closed *and* deleted #     on the exit of the context manager 

Answer 2

I think the easiest is to simply open the file in write mode and then close it. For example, if your file myfile.dat contains:

"This is the original content" 

Then you can simply write:

f = open('myfile.dat', 'w') f.close() 

This would erase all the content. Then you can write the new content to the file:

f = open('myfile.dat', 'w') f.write('This is the new content!') f.close()