reahl-parseltongue 3.1.1

Python bindings for GemStone/S 64 Bit

Parseltongue is a library that lets Python programs execute methods on objects inside a GemStone Smalltalk server.

See also

• Reference documentation

• Source code

• Other Reahl Software

Sessions

Log in by creating a session. You can choose between an RPCSession or a LinkedSession:

linked_session = LinkedSession('DataCurator', 'swordfish')

assert linked_session.is_logged_in
assert not linked_session.is_remote
assert linked_session.is_current_session

linked_session.log_out()

Multiple RPCSessions can exist simultaneously, but only a single instance of a LinkedSession is allowed per process.

Resolving objects

Looking up a Smalltalk symbol from the usual symbol dictionaries results in a GemObject object being returned which represents that object in Python:

date_class = session.resolve_symbol('Date')
assert isinstance(date_class, GemObject)

Calling methods

A GemObject object forwards method calls to its counterpart in the Gem. It returns other GemObject objects (and if the method takes arguments, those must also be GemObject objects):

today = date_class.today()
assert isinstance(today, GemObject)
assert today.isKindOf(date_class)

Transferring basic objects

Some basic objects can be transferred between GemStone and Python. These include unicode strings, various numbers and booleans:

gem_number = session.from_py(1)
long_ago = date_class.fromDays(gem_number)

long_ago_string = long_ago.asString()
python_string = long_ago_string.to_py

assert python_string == '1901/01/02'

Automatic translation of arguments

Some arguments to Gemstone method calls can be turned into GemObject instances automatically:

long_ago = date_class.fromDays(1)

long_ago_string = long_ago.asString()
python_string = long_ago_string.to_py

assert python_string == '1901/01/02'

Method name mapping

In Python, method names are spelt differently. Each ‘:’ in a Smalltalk method symbol is replaced with a ‘_’ in Python. When calling such a method, you must pass the correct number of arguments as Python positional arguments:

user_globals = session.resolve_symbol('UserGlobals')
some_key = session.new_symbol('akey')
gem_number = session.from_py(123)

user_globals.at_put(some_key, gem_number)

License

Parseltongue is licensed under the GNU Lesser General Public License v3.0 or later (LGPL-3.0-or-later).

This means you can:

• Use Parseltongue in commercial applications

• Modify Parseltongue privately

• Distribute Parseltongue as part of your applications

If you modify Parseltongue itself, you must distribute those modifications under the terms of the LGPL.

For the full license text, see the LICENSE file or visit: https://www.gnu.org/licenses/lgpl-3.0.html