code: def _istextfile(filename, blocksize=512):
  
  
      
  
      import sys
      PY3 = sys.version_info[0] == 3
  
      # A function that takes an integer in the 8-bit range and returns
      # a single-character byte object in py3 / a single-character string
      # in py2.
      #
      int2byte = (lambda x: bytes((x,))) if PY3 else chr
  
      _text_characters = (
          b''.join(int2byte(i) for i in range(32, 127)) +
          b'\n\r\t\f\b')
      block = open(filename,'rb').read(blocksize)
      if b'\x00' in block:
          # Files with null bytes are binary
          return False
      elif not block:
          # An empty file is considered a valid text file
          return True
  
      # Use translate's 'deletechars' argument to efficiently remove all
      # occurrences of _text_characters from the block
      nontext = block.translate(None, _text_characters)
      return float(len(nontext)) / len(block) <= 0.30
docs: Function found from:
          https://eli.thegreenplace.net/2011/10/19/perls-guess-if-file-is-text-or-binary-implemented-in-python
          Returns True if file is most likely a text file
          Returns False if file is most likely a binary file
          Uses heuristics to guess whether the given file is text or binary,
          by reading a single block of bytes from the file.
          If more than 30% of the chars in the block are non-text, or there
          are NUL ('\x00') bytes in the block, assume this is a binary file.