# pytds.extensions – Extensions to the DB API

## Isolation level constants

pytds.extensions.ISOLATION_LEVEL_READ_UNCOMMITTED

  Transaction can read uncommitted data

pytds.extensions.ISOLATION_LEVEL_READ_COMMITTED

  Transaction can read only committed data, will block on attempt to read modified uncommitted data

pytds.extensions.ISOLATION_LEVEL_REPEATABLE_READ

  Transaction will place lock on read records, other transactions will block trying to modify such records

pytds.extensions.ISOLATION_LEVEL_SERIALIZABLE

  Transaction will lock tables to prevent other transactions from inserting new data that would match selected recordsets

pytds.extensions.ISOLATION_LEVEL_SNAPSHOT

  Allows non-blocking consistent reads on a snapshot for transaction without blocking other transactions changes