def open(prefix_name: str, open_mode: str = "rw", **kwargs)

Opens a data partition, known as a prefix, and sets it as the current working context.

This function is the primary way to access a specific dataset within the dbzero environment. After a prefix is opened, all subsequent object creations and lookups by default (that don't specify another prefix) will occur within it.

Parameters

• prefix_name str
  The unique name for the data partition you want to open.

• open_mode {"rw", "r"}, default "rw" : str
  The mode for opening the prefix. Defaults to "rw".

  • "rw": Read-write mode. Allows both reading and modifying objects within the prefix.
  • "r": Read-only mode. Prevents any changes to the data. This is useful for preventing accidental modifications or for client applications that only need to consume data.

• **kwargs dict
  Additional keyword arguments to configure the prefix's behavior:

  • autocommit (bool): Set to False to disable automatic commits for this specific prefix. By default, it uses the global autocommit setting configured during dbzero.init().
  • slab_size (int): Specifies the size (in bytes) of the memory slab to allocate for this prefix's data. Useful for performance tuning.
  • meta_io_step_size (int): Configures the chunk size for metadata I/O operations, which can impact performance for certain workloads.
  • lock_flags (dict): Configure locking behavior when opening the prefix in read-write mode.

Returns

This method does not return any value.

Examples

Basic Usage

Open a prefix in the default read-write mode. This becomes the current active prefix.

# Initialize dbzero first
db0.init("app-data")
 
# Open a prefix for read-write access
db0.open("user-profiles")
 
# Now you can work with objects in the "user-profiles" prefix
user = UserProfile(name="Alex")

Opening in Read-Only Mode

Open a prefix for safe, read-only access. This is ideal for analytics or recovery operations.

# Open the same prefix, but only for reading
db0.open("user-profiles", "r")
 
# This will succeed
alex = next(iter(db0.find(UserProfile, "Alex")))
 
# This will raise an error because the prefix is read-only
alex.last_login = datetime.now()
db0.commit()

Customizing Prefix Settings

You can override global configurations on a per-prefix basis. Here, we disable autocommit for a specific prefix that requires manual transaction control.

# Open a prefix and disable autocommit just for it
db0.open("transaction-logs", autocommit=False)
 
# Changes made here won't be saved until you manually call db0.commit()
log_entry = Log(message="User action")
 
# No autocommit happens here
time.sleep(1)
 
# Manually commit the changes
db0.commit()