From 8cd70975854ddefaf9dadbade1559059ad781f3c Mon Sep 17 00:00:00 2001
From: Timotej Lazar <timotej.lazar@araneo.org>
Date: Fri, 28 Aug 2015 11:47:53 +0200
Subject: Add Python session support

---
 server/python_session.py | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 server/user_session.py   | 11 +++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 server/python_session.py

diff --git a/server/python_session.py b/server/python_session.py
new file mode 100644
index 0000000..7a5d22a
--- /dev/null
+++ b/server/python_session.py
@@ -0,0 +1,47 @@
+# coding=utf-8
+
+import threading
+import python.engine
+
+__all__ = ['PythonSession']
+
+class PythonSession(object):
+    """Abstracts a Python session.
+    Only public methods are available to the outside world due to the use of multiprocessing managers.
+    Therefore prefix any private methods with an underscore (_).
+    No properties are accessible; use getters and setters instead.
+    Values are passed by value instead of by reference (deep copy!).
+    """
+    def __init__(self):
+        self._access_lock = threading.Lock()
+        self._interpreter = None
+
+    def create(self):
+        with self._access_lock:
+            if not self._interpreter:
+                self._interpreter = python.engine.create()
+
+    def pull(self):
+        with self._access_lock:
+            if self._interpreter is None:
+                return 'Python is not running'
+            return python.engine.pull(self._interpreter)
+
+    def push(self, stdin):
+        with self._access_lock:
+            if self._interpreter is not None:
+                python.engine.push(self._interpreter, stdin)
+
+    def destroy(self):
+        with self._access_lock:
+            if self._interpreter is not None:
+                python.engine.destroy(self._interpreter)
+                self._interpreter = None
+
+    def __del__(self):
+        if hasattr(self, '_interpreter') and self._interpreter is not None:
+            python.engine.destroy(self._interpreter)
+            self._interpreter = None
+
+    def test(self, user_id, problem_id, program):
+        return ['Python testing is not implemented yet']
diff --git a/server/user_session.py b/server/user_session.py
index c9d21b4..0abc421 100644
--- a/server/user_session.py
+++ b/server/user_session.py
@@ -6,6 +6,7 @@ import hashlib
 import base64
 import random
 from . import prolog_session
+from . import python_session
 from . import problems
 import db
 from errors.session import NoSuchSession, AuthenticationFailed
@@ -30,6 +31,7 @@ class UserSession(object):
         self.uid = uid
         self.username = username
         self.prolog_session = None
+        self.python_session = None
 
     def destroy(self):
         """Destroys the session."""
@@ -39,6 +41,9 @@ class UserSession(object):
             if self.prolog_session is not None:
                 self.prolog_session.end()
                 self.prolog_session = None
+            if self.python_session is not None:
+                self.python_session.end()
+                self.python_session = None
             # TODO: add any cleanups as features are added!
 
     def get_sid(self):
@@ -53,6 +58,12 @@ class UserSession(object):
                 self.prolog_session = prolog_session.PrologSession()  # lazy init
             return self.prolog_session
 
+    def get_python(self):
+        with self._access_lock:
+            if self.python_session is None:
+                self.python_session = python_session.PythonSession()  # lazy init
+            return self.python_session
+
     def get_problem_data(self, language, problem_group, problem):
         mod = problems.load_problem(language, problem_group, problem, 'en')
         conn = db.get_connection()
-- 
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