"psycopg2.errorcodes" – Error codes defined by PostgreSQL
*********************************************************

Added in version 2.0.6.

This module contains symbolic names for all PostgreSQL error codes and
error classes codes.  Subclasses of "Error" make the PostgreSQL error
code available in the "pgcode" attribute.

From PostgreSQL documentation:

   All messages emitted by the PostgreSQL server are assigned five-
   character error codes that follow the SQL standard’s conventions
   for "SQLSTATE" codes.  Applications that need to know which error
   condition has occurred should usually test the error code, rather
   than looking at the textual error message.  The error codes are
   less likely to change across PostgreSQL releases, and also are not
   subject to change due to localization of error messages. Note that
   some, but not all, of the error codes produced by PostgreSQL are
   defined by the SQL standard; some additional error codes for
   conditions not defined by the standard have been invented or
   borrowed from other databases.

   According to the standard, the first two characters of an error
   code denote a class of errors, while the last three characters
   indicate a specific condition within that class. Thus, an
   application that does not recognize the specific error code can
   still be able to infer what to do from the error class.

See also: PostgreSQL Error Codes table

An example of the available constants defined in the module:

>>> errorcodes.CLASS_SYNTAX_ERROR_OR_ACCESS_RULE_VIOLATION
'42'
>>> errorcodes.UNDEFINED_TABLE
'42P01'

Constants representing all the error values defined by PostgreSQL
versions between 8.1 and 15 are included in the module.

psycopg2.errorcodes.lookup(code)

   Lookup an error code or class code and return its symbolic name.

   Raise "KeyError" if the code is not found.

      >>> try:
      ...     cur.execute("SELECT ouch FROM aargh;")
      ... except Exception as e:
      ...     pass
      ...
      >>> errorcodes.lookup(e.pgcode[:2])
      'CLASS_SYNTAX_ERROR_OR_ACCESS_RULE_VIOLATION'
      >>> errorcodes.lookup(e.pgcode)
      'UNDEFINED_TABLE'

   Added in version 2.0.14.
