Python securely remove file

Question

How can I securely remove a file using python? The function os.remove(path) only removes the directory entry, but I want to securely remove the file, similar to the apple feature called "Secure Empty Trash" that randomly overwrites the file.

What function securely removes a file using this method?

Answer 1

You can use srm to securely remove files. You can use Python's os.system() function to call srm.

Answer 2

So at least in Python 3 using @kindall's solution I only got it to append. Meaning the entire contents of the file were still intact and every pass just added to the overall size of the file. So it ended up being [Original Contents][Random Data of that Size][Random Data of that Size][Random Data of that Size] which is not the desired effect obviously.

This trickery worked for me though. I open the file in append to find the length, then reopen in r+ so that I can seek to the beginning (in append mode it seems like what caused the undesired effect is that it was not actually possible to seek to 0)

So check this out:

def secure_delete(path, passes=3):
with open(path, "ba+", buffering=0) as delfile:
    length = delfile.tell()
delfile.close()
with open(path, "br+", buffering=0) as delfile:
    #print("Length of file:%s" % length)
    for i in range(passes):
        delfile.seek(0,0)
        delfile.write(os.urandom(length))
        #wait = input("Pass %s Complete" % i)
    #wait = input("All %s Passes Complete" % passes)
    delfile.seek(0)
    for x in range(length):
        delfile.write(b'\x00')
    #wait = input("Final Zero Pass Complete")
os.remove(path) #So note here that the TRUE shred actually renames to file to all zeros with the length of the filename considered to thwart metadata filename collection, here I didn't really care to implement

Un-comment the prompts to check the file after each pass, this looked good when I tested it with the caveat that the filename is not shredded like the real shred -zu does