feat(api): add .tables accessor to BaseBackend

Author: jcrist

ibis/backends/base/__init__.py

@@ -1,10 +1,20 @@
 from __future__ import annotations
 
 import abc
+import collections.abc
 import functools
+import keyword
 import re
 from pathlib import Path
-from typing import TYPE_CHECKING, Any, Callable, ClassVar, Iterable, Mapping
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Callable,
+    ClassVar,
+    Iterable,
+    Iterator,
+    Mapping,
+)
 
 if TYPE_CHECKING:
     import pandas as pd
@@ -145,6 +155,55 @@ def list_tables(self, like=None):
         return self.client.list_tables(like, database=self.name)
 
 
+class TablesAccessor(collections.abc.Mapping):
+    """A mapping-like object for accessing tables off a backend.
+
+    Tables may be accessed by name using either index or attribute access:
+
+    Examples
+    --------
+    >>> con = ibis.sqlite.connect("example.db")
+    >>> people = con.tables['people']  # access via index
+    >>> people = con.tables.people  # access via attribute
+    """
+
+    def __init__(self, backend: BaseBackend):
+        self._backend = backend
+
+    def __getitem__(self, name) -> ir.Table:
+        try:
+            return self._backend.table(name)
+        except Exception as exc:
+            raise KeyError(name) from exc
+
+    def __getattr__(self, name) -> ir.Table:
+        if name.startswith("_"):
+            raise AttributeError(name)
+        try:
+            return self._backend.table(name)
+        except Exception as exc:
+            raise AttributeError(name) from exc
+
+    def __iter__(self) -> Iterator[str]:
+        return iter(sorted(self._backend.list_tables()))
+
+    def __len__(self) -> int:
+        return len(self._backend.list_tables())
+
+    def __dir__(self) -> list[str]:
+        o = set()
+        o.update(dir(type(self)))
+        o.update(
+            name
+            for name in self._backend.list_tables()
+            if name.isidentifier() and not keyword.iskeyword(name)
+        )
+        return list(o)
+
+    def _ipython_key_completions_(self) -> list[str]:
+        return self._backend.list_tables()
+
+
 class BaseBackend(abc.ABC):
     """Base backend class.
 
@@ -368,6 +427,20 @@ def exists_table(self, name: str, database: str | None = None) -> bool:
     def table(self, name: str, database: str | None = None) -> ir.Table:
         """Return a table expression from the database."""
 
+    @functools.cached_property
+    def tables(self):
+        """An accessor for tables in the database.
+
+        Tables may be accessed by name using either index or attribute access:
+
+        Examples
+        --------
+        >>> con = ibis.sqlite.connect("example.db")
+        >>> people = con.tables['people']  # access via index
+        >>> people = con.tables.people  # access via attribute
+        """
+        return TablesAccessor(self)
+
     @deprecated(version='2.0', instead='use `.table(name).schema()`')
     def get_schema(self, table_name: str, database: str = None) -> sch.Schema:
         """Return the schema of `table_name`."""

ibis/backends/tests/test_api.py

@@ -1,5 +1,7 @@
 import pytest
 
+import ibis
+
 
 def test_backend_name(backend):
     # backend is the TestConf for the backend
@@ -41,6 +43,39 @@ def test_database_consistency(con):
 def test_list_tables(con):
     tables = con.list_tables()
     assert isinstance(tables, list)
-    # only table that is garanteed to be in all backends
+    # only table that is guaranteed to be in all backends
     assert 'functional_alltypes' in tables
     assert all(isinstance(table, str) for table in tables)
+
+
+def test_tables_accessor_mapping(con):
+    assert isinstance(con.tables["functional_alltypes"], ibis.ir.Table)
+
+    with pytest.raises(KeyError, match="doesnt_exist"):
+        con.tables["doesnt_exist"]
+
+    tables = con.list_tables()
+
+    assert len(con.tables) == len(tables)
+    assert sorted(con.tables) == sorted(tables)
+
+
+def test_tables_accessor_getattr(con):
+    assert isinstance(con.tables.functional_alltypes, ibis.ir.Table)
+
+    with pytest.raises(AttributeError, match="doesnt_exist"):
+        getattr(con.tables, "doesnt_exist")
+
+    # Underscore/double-underscore attributes are never available, since many
+    # python apis expect checking for the absence of these to be cheap.
+    with pytest.raises(AttributeError, match="_private_attr"):
+        getattr(con.tables, "_private_attr")
+
+
+def test_tables_accessor_tab_completion(con):
+    attrs = dir(con.tables)
+    assert 'functional_alltypes' in attrs
+    assert 'keys' in attrs  # type methods also present
+
+    keys = con.tables._ipython_key_completions_()
+    assert 'functional_alltypes' in keys