Append common actions to the PandasClient

This pull request adds list_tables, load_data, and create_table
attributes for the PandasClient.

Author: tonyfast <tony.fast@gmail.com>

Closes ibis-project#1464 from tonyfast/pandas-ddl and squashes the following commits:

cd045b5 [tonyfast] Fix flake spacings
fd92308 [tonyfast] Merge remote-tracking branch 'ibis/master' into pandas-ddl
9e0f582 [tonyfast] Include a get_schema attribute and tests for create_table
9490ddd [tonyfast] Merge remote-tracking branch 'ibis/master' into pandas-ddl
dc3bb12 [tonyfast] A simpler exists_table method
5647eea [tonyfast] Resolve some flake8 issues
88997b1 [tonyfast] Add a test for list_tables(like="")
4dd37af [tonyfast] Add a get_schema method to the pandas client and fix for review
9db2db3 [tonyfast] Add spaces after function definition and simplify list_tables test.
def4e16 [tonyfast] Include tests for loading data with the pandas backend.
9d7aad7 [tonyfast] Add list_tables, load_data, and create_table to the pandas client

ibis/pandas/client.py

@@ -1,5 +1,6 @@
 from __future__ import absolute_import
 
+import re
 import six
 import toolz
 import numpy as np
@@ -9,6 +10,7 @@
 from multipledispatch import Dispatcher
 
 import ibis.client as client
+import ibis.common as com
 import ibis.expr.types as ir
 import ibis.expr.schema as sch
 import ibis.expr.datatypes as dt
@@ -321,6 +323,68 @@ def compile(self, expr, *args, **kwargs):
     def database(self, name=None):
         return PandasDatabase(name, self)
 
+    def list_tables(self, like=None):
+        tables = list(self.dictionary.keys())
+        if like is not None:
+            pattern = re.compile(like)
+            return list(filter(lambda t: pattern.findall(t), tables))
+        return tables
+
+    def load_data(self, table_name, obj, **kwargs):
+        """
+        Parameters
+        ----------
+        table_name : string
+        obj: pandas.DataFrame
+        """
+        # kwargs is a catch all for any options required by other backends.
+        self.dictionary[table_name] = pd.DataFrame(obj)
+
+    def create_table(self, table_name, obj=None, schema=None):
+        if obj is None and schema is None:
+            raise com.IbisError('Must pass expr or schema')
+
+        if obj is not None:
+            df = pd.DataFrame(obj)
+        else:
+            dtypes = ibis_schema_to_pandas(schema)
+            df = schema.apply_to(
+                pd.DataFrame(columns=list(map(toolz.first, dtypes)))
+            )
+
+        self.dictionary[table_name] = df
+
+    def get_schema(self, table_name, database=None):
+        """
+        Return a Schema object for the indicated table and database
+
+        Parameters
+        ----------
+        table_name : string
+          May be fully qualified
+        database : string, default None
+
+        Returns
+        -------
+        schema : ibis Schema
+        """
+        return sch.infer(self.dictionary[table_name])
+
+    def exists_table(self, name):
+        """
+        Determine if the indicated table or view exists
+
+        Parameters
+        ----------
+        name : string
+        database : string, default None
+
+        Returns
+        -------
+        if_exists : boolean
+        """
+        return bool(self.list_tables(like=name))
+
     @property
     def version(self):
         return parse_version(pd.__version__)

ibis/pandas/tests/test_client.py

@@ -36,12 +36,31 @@ def test_client_table_repr(table):
     assert 'PandasTable' in repr(table)
 
 
+def test_load_data(client):
+    client.load_data('testing', tm.makeDataFrame())
+    assert client.exists_table('testing')
+    assert client.get_schema('testing')
+
+
+def test_create_table(client):
+    client.create_table('testing', obj=tm.makeDataFrame())
+    assert client.exists_table('testing')
+    client.create_table('testingschema', schema=client.get_schema('testing'))
+    assert client.exists_table('testingschema')
+
+
 def test_literal(client):
     lit = ibis.literal(1)
     result = client.execute(lit)
     assert result == 1
 
 
+def test_list_tables(client):
+    assert client.list_tables(like='df_unknown')
+    assert not client.list_tables(like='not_in_the_database')
+    assert client.list_tables()
+
+
 def test_read_with_undiscoverable_type(client):
     with pytest.raises(TypeError):
         client.table('df_unknown')