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4.9.1.1 Codec Objects

The `Codec` class defines these methods which also define the function interfaces of the stateless encoder and decoder:

`encode`( | input[, errors])

  Encodes the object input and returns a tuple (output object, length consumed). While codecs are not restricted to use with Unicode, in a Unicode context, encoding converts a Unicode object to a plain string using a particular character set encoding (e.g., `cp1252` or `iso-8859-1`).

  errors defines the error handling to apply. It defaults to `'strict'` handling.

  The method may not store state in the `Codec` instance. Use `StreamCodec` for codecs which have to keep state in order to make encoding/decoding efficient.

  The encoder must be able to handle zero length input and return an empty object of the output object type in this situation.

`decode`( | input[, errors])

  Decodes the object input and returns a tuple (output object, length consumed). In a Unicode context, decoding converts a plain string encoded using a particular character set encoding to a Unicode object.

  input must be an object which provides the `bf_getreadbuf` buffer slot. Python strings, buffer objects and memory mapped files are examples of objects providing this slot.

  errors defines the error handling to apply. It defaults to `'strict'` handling.

  The method may not store state in the `Codec` instance. Use `StreamCodec` for codecs which have to keep state in order to make encoding/decoding efficient.

  The decoder must be able to handle zero length input and return an empty object of the output object type in this situation.

The `StreamWriter` and `StreamReader` classes provide generic working interfaces which can be used to implement new encodings submodules very easily. See `encodings.utf_8` for an example of how this is done.