delete blank or empty lines in the text file for closed code

If you want to remove blank lines from an existing file without writing to a new one, you can open the same file again in read-write mode (denoted by 'r+') for writing. Truncate the file at the write position after the writing is done:

with open('file.txt') as reader, open('file.txt', 'r+') as writer:
  for line in reader:
    if line.strip():
      writer.write(line)
  writer.truncate()

Demo: https://repl.it/@blhsing/KaleidoscopicDarkredPhp