Handling PyMySql exceptions - Best Practices
Solution 1
there is very generic way to use pymysql error handling. I am using this for sqlutil module. This way you can catch all your errors raised by pymysql without thinking about its type.
try:
connection.close()
print("connection closed successfully")
except pymysql.Error as e:
print("could not close connection error pymysql %d: %s" %(e.args[0], e.args[1]))
Solution 2
You cannot specify an expect clause based on an exception instance attribute obviously, and not even on an exception class attribute FWIW - it only works on exception type.
A solution to your problem is to have two nested try/except blocks, the inner one handling duplicate entries and re-raising other IntegrityError
s, the outer one being the generic case:
try:
try:
cur.execute(query, values)
except IntegrityError as e:
if e.args[0] == PYMYSQL_DUPLICATE_ERROR:
handle_duplicate_pymysql_exception(e, func_a)
else:
raise
except Exception as e:
handle_unknown_pymysql_exception(e, func_b)
Whether this is better than having a duplicate call to handle_unknown_pymysql_exception
is up to you...
oria general
Updated on June 24, 2022Comments
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oria general almost 2 years
My question regards exception best practices. I'll present my question on a specific case with PyMySQL but it regards errors handling in general. I am using PyMySQL and out of the many possible exceptions, there is one I want to deal with in a specific manner. "Duplicate" exception.
pymysql maps mysql errors to python errors according to the following table:
_map_error(ProgrammingError, ER.DB_CREATE_EXISTS, ER.SYNTAX_ERROR, ER.PARSE_ERROR, ER.NO_SUCH_TABLE, ER.WRONG_DB_NAME, ER.WRONG_TABLE_NAME, ER.FIELD_SPECIFIED_TWICE, ER.INVALID_GROUP_FUNC_USE, ER.UNSUPPORTED_EXTENSION, ER.TABLE_MUST_HAVE_COLUMNS, ER.CANT_DO_THIS_DURING_AN_TRANSACTION) _map_error(DataError, ER.WARN_DATA_TRUNCATED, ER.WARN_NULL_TO_NOTNULL, ER.WARN_DATA_OUT_OF_RANGE, ER.NO_DEFAULT, ER.PRIMARY_CANT_HAVE_NULL, ER.DATA_TOO_LONG, ER.DATETIME_FUNCTION_OVERFLOW) _map_error(IntegrityError, ER.DUP_ENTRY, ER.NO_REFERENCED_ROW, ER.NO_REFERENCED_ROW_2, ER.ROW_IS_REFERENCED, ER.ROW_IS_REFERENCED_2, ER.CANNOT_ADD_FOREIGN, ER.BAD_NULL_ERROR) _map_error(NotSupportedError, ER.WARNING_NOT_COMPLETE_ROLLBACK, ER.NOT_SUPPORTED_YET, ER.FEATURE_DISABLED, ER.UNKNOWN_STORAGE_ENGINE) _map_error(OperationalError, ER.DBACCESS_DENIED_ERROR, ER.ACCESS_DENIED_ERROR, ER.CON_COUNT_ERROR, ER.TABLEACCESS_DENIED_ERROR, ER.COLUMNACCESS_DENIED_ERROR)
I want to specifically catch ER.DUP_ENTRY but I only know how to catch IntegrityError and that leads to redundant cases within my exception catch.
cur.execute(query, values) except IntegrityError as e: if e and e[0] == PYMYSQL_DUPLICATE_ERROR: handel_duplicate_pymysql_exception(e, func_a) else: handel_unknown_pymysql_exception(e, func_b) except Exception as e: handel_unknown_pymysql_exception(e, func_b)
Is there a way to simply catch only ER.DUP_ENTRY some how? looking for something like:
except IntegrityError.DUP_ENTRY as e: handel_duplicate_pymysql_exception(e, func_a)
Thanks in advance for your guidance,
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Nasif Imtiaz Ohi almost 4 yearsPYMYSQL_DUPLICATE_ERROR code is 1062. I had to set that in my code and e.args[0] is only an integer value.