python - SQLAlchemy execute() return ResultProxy as Tuple, not dict

Question

I have the following code:

query = """
SELECT Coalesce((SELECT sp.param_value
                 FROM   sites_params sp
                 WHERE  sp.param_name = 'ci'
                        AND sp.site_id = s.id
                 ORDER  BY sp.id DESC
                 LIMIT  1), -1) AS ci
FROM   sites s
WHERE  s.deleted = 0
       AND s.id = 10 

"""

site = db_session.execute(query)
# print site 
# <sqlalchemy.engine.result.ResultProxy object at 0x033E63D0>

site = db_session.execute(query).fetchone()
print site  # (u'375')
print list(site) # [u'375']

Why does SQLAlchemy return tuples, not dicts, for this query? I want to use the following style to access the results of the query:

print site.ci
# u'375'

Answer 1

This is an old question, but still relevant today. Getting SQL Alchemy to return a dictionary is very useful, especially when working with RESTful based APIs that return JSON.

Here is how I did it using the db_session in Python 3:

resultproxy = db_session.execute(query)

d, a = {}, []
for rowproxy in resultproxy:
    # rowproxy.items() returns an array like [(key0, value0), (key1, value1)]
    for column, value in rowproxy.items():
        # build up the dictionary
        d = {**d, **{column: value}}
    a.append(d)

The end result is that the array a now contains your query results in dictionary format.

As for how this works in SQL Alchemy:

• Thedb_session.execute(query) returns a ResultProxy object
• The ResultProxy object is made up of RowProxy objects
• The RowProxy object has an .items() method that returns key, value tuples of all the items in the row, which can be unpacked as key, value in a for operation.

And here a one-liner alternative:

[{column: value for column, value in rowproxy.items()} for rowproxy in resultproxy]

From the docs:

class sqlalchemy.engine.RowProxy(parent, row, processors, keymap)

Proxy values from a single cursor row.

Mostly follows “ordered dictionary” behavior, mapping result values to the string-based column name, the integer position of the result in the row, as well as Column instances which can be mapped to the original Columns that produced this result set (for results that correspond to constructed SQL expressions).

has_key(key) Return True if this RowProxy contains the given key.

items() Return a list of tuples, each tuple containing a key/value pair.

keys() Return the list of keys as strings represented by this RowProxy.

Link: http://docs.sqlalchemy.org/en/latest/core/connections.html#sqlalchemy.engine.RowProxy.items