code: def compress(pub):
      '''
      Input must be hex string, and a valid uncompressed public key.
      Check if it's a valid key first, using the validatepubkey()
      function below, and then verify that the str len is 130.
      '''
  
      x = pub[2:66]
      y = pub[66:]
      if int(y,16) % 2:
          o = str('03') + str(x)
      else:
          o = str('02') + str(x)
      return f compress(pub):
      '''
      Input must be hex string, and a valid uncompressed public key.
      Check if it's a valid key first, using the validatepubkey()
      function below, and then verify that the str len is 130.
      '''
  
      x = pub[2:66]
      y = pub[66:]
      if int(y,16) % 2:
          o = str('03') + str(x)
      else:
          o = str('02') + str(x)
      return o
docs: Input must be hex string, and a valid uncompressed public key.
      Check if it's a valid key first, using the validatepubkey()
      function below, and then verify that the str len is 130.