Eliminate footer and header information from multiple text files (why can't I eliminate the last line as easily as I can eliminate the first lines?)

I have been trying all day.

# successfully writes the data from line 17 and next lines 
# to new (temp) file named and saved in the os

import os
import glob

files = glob.glob('/Users/path/Documents/test/*.txt')
for myspec in files:
    temp_filename = 'foo.temp.txt'
    with open(myspec) as f:
        for n in range(17):
            f.readline()
        with open(temp_filename, 'w') as w:
            w.writelines(f)
    os.remove(myspec)
    os.rename(temp_filename, myspec)

# delete original file and rename the temp file so it replaces the original file
print("done")

The above works and it works well! I love it. I am very happy.

But this below does NOT work (same files, I am preprocessing files) :

# trying unsuccessfully to remove the last line which is line 
# 2048 in all files and save again like above


import os
import glob

files = glob.glob('/Users/path/Documents/test/*.txt')
for myspec in files:
    temp_filename = 'foo.temp.txt'
    with open(myspec) as f:
        for n in range(-1):
            f.readline()
        with open(temp_filename, 'w') as w:
            w.writelines(f)
    os.remove(myspec)
    os.rename(temp_filename, myspec)

# delete original file and rename the temp file so it replaces the original file
print("done")

This does not work. It doesn't give an error, it prints done, but it does not change the file. I have tried range(-1), all the way up to range(-7), thinking maybe there were blank lines at the end I could not see. This is the only difference between the two blocks of code. If anyone could help that would be great.

To summarize, I got rid of permanently the headers and now I still have a 1 line footer I can not get rid of permanently.

Thank you so much for any help. I need to write permanently edited files. Because I have a ton of code that wants 2 or 3 column files without all the header footer junk, and the junk and file types vary widely. So if I lose the junk permanently ASCII can guess correctly the file types. And I really do not want to try and rewrite that code right now, it's very complicated and involves uncertainty and it took me months to get working correctly. I don't read the files until I'm inside a function and there are many files that are displayed in multiple drop downs. Thank you! All day I've been at this, I have tried other methods. I'd like to make THIS the above method work. To pop off the last and write it back to a permanent file. It doesn't like the -1. Right now it is just one specific line, it is (specifically line 2048 after the header is removed.) Therefore just removing line 2048 would be fine too. Its the last line of the files which are a batch of TSV files that are CCD readouts. Thanks in advance!