bytes() and bytearray() don't show the default values for source, encoding and errors as shown below:

class bytearray(source=b'')
class bytearray(source, encoding)
class bytearray(source, encoding, errors)

class bytes(source=b'')
class bytes(source, encoding)
class bytes(source, encoding, errors)

So, they should have the default values as shown below:

class bytearray(source=b'')
class bytearray(source, encoding='utf-8')
class bytearray(source, encoding='utf-8', errors='strict')

class bytes(source=b'')
class bytes(source, encoding='utf-8')
class bytes(source, encoding='utf-8', errors='strict')