7.4.6 Delete Datastore Objects

The oml.ds.delete function deletes datastores or objects in a datastore.

Use the oml.ds.delete function to delete one or more datastores in your database schema or to delete objects in a datastore.

The syntax of oml.ds.delete is the following:

oml.ds.delete(name, objs=None, regex_match=False)

The argument to the name parameter may be one of the following:

• A string that specifies the name of the datastore to modify or delete, or a regular expression that matches the datastores to delete.

• A list of str objects that name the datastores from which to delete objects.

The objs parameter specifies the objects to delete from a datastore. The argument to the objs parameter may be one of the following:

• A string that specifies the object to delete from one or more datastores, or a regular expression that matches the objects to delete.

• None (the default), which deletes the entire datastore or datastores.

The regex_match parameter is a bool that indicates whether the name or objs arguments are regular expressions. The default value is False. The regex_match parameter operates as follows:

• If regex_match=False and if name is not None, and:

  • If objs=None, then oml.ds.delete deletes the datastore or datastores specified in the name argument.

  • If you specify one or more datastores with the name argument and one or more datastore objects with the objs argument, then oml.ds.delete deletes the specified Python objects from the datastores.

• If regex_match=True and:

  • If objs=None, then oml.ds.delete deletes the datastores you specified in the name argument.

  • If the name argument is a string and you specify one or more datastore objects with the objs argument, then oml.ds.delete deletes from the datastore the objects whose names match the regular expression specified in the objs argument.

  • If the name argument is a list of str objects, then the objs argument must be a list of str objects of the same length as name, and oml.ds.delete deletes from the datastores the objects whose names match the regular expressions specified in objs.

This function raises an error if the following occur:

• A specified datastore does not exist.

• Argument regex_match is False and argument name is a list of str objects larger than 1 and argument objs is not None.

• Argument regex_match is True and arguments name and objs are lists that are not the same length.

Example 7-18 Deleting Datastore Objects

This example demonstrates the using the oml.ds.delete function. For the creation of the datastores used in this example, see Example 7-14.

import oml

# Show the existing datastores.
oml.ds.dir()

# Show the Python objects in the ds_pydata datastore.
oml.ds.describe(name='ds_pydata')

# Delete some objects from the datastore.
oml.ds.delete(name="ds_pydata", objs=["wine", "oml_boston"])

# Delete a datastore.
oml.ds.delete(name="ds_pydata")

# Delete all datastores whose names match a pattern.
oml.ds.delete(name="_pymodel", regex_match=True)

# Show the existing datastores again.
oml.ds.dir()

Listing for This Example

>>> import oml
>>> 
>>> # Show the existing datastores.
... oml.ds.dir()
  datastore_name  object_count  size                date      description
0      ds_pydata             3  26214 2019-05-18 21:04:06  python datasets
1     ds_pymodel             2   6370 2019-05-18 21:08:18             None
2   ds_wine_data             1   1410 2019-05-18 21:06:53     wine dataset
>>>
>>> # Show the Python objects in the ds_pydata datastore.
... oml.ds.describe(name='ds_pydata')
    object_name          class  size  length  row_count  col_count
0    oml_boston  oml.DataFrame   1073     506        506         14
1  oml_diabetes  oml.DataFrame    964     442        442         11
2          wine          Bunch  24177       5          1          5
>>> 
>>> # Delete some objects from a datastore.
... oml.ds.delete(name="ds_pydata", objs=["wine", "oml_boston"])
{'wine', 'oml_boston'}
>>>
>>> # Delete a datastore.
... oml.ds.delete(name="ds_pydata")
'ds_pydata'
>>> 
>>> # Delete all datastores whose names match a pattern.
... oml.ds.delete(name="_pymodel", regex_match=True)
{'ds_pymodel'}
>>> 
>>> # Show the existing datastores again.
... oml.ds.dir()
  datastore_name  object_count  size                date   description
0   ds_wine_data             1  1410 2019-05-18 21:06:53  wine dataset