When combined with the connector, Pandas can be used to generate data frames that contain your Google Spanner data. Once created, a data frame can be passed to various other Python packages.

Connecting

Pandas relies on an SQLAlchemy engine to execute queries. Before you can use Pandas you must import it:

import pandas as pd
from sqlalchemy import create_engine
engine = create_engine("googlespanner:///?ProjectId='project1';InstanceId='instance1';Database='db1';OAuthClientId='757060765381';OauthClientSecret='abc';")

Querying Data

In Pandas, SELECT queries are provided in a call to the read_sql() method, alongside a relevant connection object. Pandas executes the query on that connection, and returns the results in the form of a data frame, which can be used for a variety of purposes.

df = pd.read_sql("""
	SELECT
	   Name,
	   TotalDue,
     $exNumericCol;
	FROM [CData].[GoogleSpanner].Customer;""", engine)
print(df)

Modifying Data

To insert new records into a table, create a new data frame, and define its fields accordingly. When that is done, call to_sql() on the data frame to perform the INSERT operation with the connector, as shown in the example below. You must set the "if _exists" argument to "append" to prevent Pandas from attempting building the table from scratch. To prevent Pandas from writing the data frame index as a column, set index=False.

df = pd.DataFrame({"Name": ["Jon Doe"], "TotalDue": ["John"]})
df.to_sql("[CData].[GoogleSpanner].Customer", con=engine, if_exists="append", index=False)