better understanding

docs/subinterpreters/basic_communication.py

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+# to run on command line to see result, not on IDLE
+import os
+import os.path
+import pickle
+from threading import Thread
+import interpreters
+
+
+SCRIPT_DIR = os.path.dirname(__file__)
+
+
+def section_header(label):
+    print()
+    print('####################')
+    print(f'# {label}')
+    print('####################')
+    print()
+
+
+#############################
+
+interp = interpreters.create()
+
+interp.run(f'''if True:
+    def get_question(answer):
+        return '<question for {{}}>'.format(answer)
+    ''')
+
+interp.run(f'''if True:
+    import os
+    import pickle
+
+    def handle_data(data):
+        print('handling data: {{!r}}'.format(data))
+    ''')
+
+
+#############################
+
+section_header('example 1')
+
+"""
+>>> data1, data2 = 42, 'spam'
+>>> interp.run(f'''if True:
+...     q = get_question({data1})
+...     write(q)
+...     write({data2!r})
+...     ''')
+"""
+
+data1, data2 = 42, 'spam'
+interp.run(f'''if True:
+    q = get_question({data1})
+    print(q)
+    print({data2!r})
+    ''')
+
+
+#############################
+
+section_header('example 2')
+
+"""
+>>> r, w = os.pipe()
+>>> def handler():
+...     interp.run(f'''if True:
+...         handle_data( os.read({r}, 100) )
+...         ''')
+...
+>>> Thread(target=handler).start()
+>>> os.write(w, b'spam')
+"""
+
+r, w = os.pipe()
+
+def handler():
+    interp.run(f'''if True:
+        data = os.read({r}, 100)
+        handle_data(data)
+        ''')
+
+t = Thread(target=handler)
+t.start()
+
+os.write(w, b'spam')
+
+t.join()
+os.close(r)
+os.close(w)
+
+
+#############################
+
+section_header('example 3')
+
+"""
+>>> r, w = os.pipe()
+>>> r2, w2 = os.pipe()
+>>> def handler():
+...     interp.run(f'''if True:
+...         data = os.read({r}, 100)
+...         while True:
+...             handle_data(data)
+...             os.write({w2}, b'<ACK>')
+...             data = os.read({r}, 100)
+...         ''')
+...
+>>> Thread(target=handler).start()
+>>> os.write(w, b'spam')
+>>> os.read(r2, 100)
+"""
+
+r, w = os.pipe()
+r2, w2 = os.pipe()
+
+def handler():
+    interp.run(f'''if True:
+        data = os.read({r}, 100)
+        while data != b'<DONE>':
+            handle_data(data)
+            os.write({w2}, data)
+            data = os.read({r}, 100)
+        print('handler done!')
+        ''')
+
+t = Thread(target=handler)
+t.start()
+
+os.write(w, b'spam')
+assert os.read(r2, 100) == b'spam'
+os.write(w, b'eggs')
+assert os.read(r2, 100) == b'eggs'
+os.write(w, b'<DONE>')
+
+t.join()
+os.close(r)
+os.close(w)
+os.close(r2)
+os.close(w2)
+
+
+#############################
+
+section_header('example 4')
+
+"""
+>>> r, w = os.pipe()
+>>> def handler():
+...     interp.run(f'''if True:
+...         data = pickle.load( os.open({r}) )
+...         handle_data(data)
+...         ''')
+...
+>>> Thread(target=handler).start()
+>>> pickle.dump('spam', os.open(w, 'w'))
+"""
+
+r, w = os.pipe()
+r2, w2 = os.pipe()
+
+def handler():
+    interp.run(f'''if True:
+        data = os.read({r}, 100)
+        while data != b'<DONE>':
+            data = pickle.loads(data)
+            handle_data(data)
+            os.write({w2}, data if isinstance(data, bytes) else data.encode('utf-8'))
+            data = os.read({r}, 100)
+        #with os.fdopen({r}, 'rb') as infile:
+        #    data = pickle.load(infile)
+        #    while data != b'<DONE>':
+        #        os.write({w2}, data if isinstance(data, bytes) else data.encode('utf-8'))
+        #        handle_data(data)
+        #        data = pickle.load(infile)
+        print('handler done!')
+        ''')
+
+t = Thread(target=handler)
+t.start()
+
+os.write(w, pickle.dumps('spam'))
+assert (v := os.read(r2, 100)) == b'spam', v
+os.write(w, pickle.dumps('eggs'))
+assert (v := os.read(r2, 100)) == b'eggs', v
+os.write(w, b'<DONE>')
+#with os.fdopen(w, 'wb') as outfile:
+#    pickle.dump('spam', outfile)
+#    assert os.read(r2, 100) == 'spam'
+#    pickle.dump('eggs', outfile)
+#    assert os.read(r2, 100) == 'eggs'
+#    pickle.dump(b'<DONE>', outfile)
+
+t.join()
+os.close(r2)
+os.close(w2)
+
+
+#############################
+
+section_header('example 5')
+
+"""
+>>> rch, sch = channels.create()
+>>> def handler():
+...     interp.run('''if True:
+...         while True:
+...             handle_data( rch.recv() )
+...         ''', channels={'rch': rch})
+...
+>>> Thread(target=handler).start()
+>>> sch.send(b'spam')
+"""
+
+#rch, sch = interpreters.create_channel()
+#
+#def handler():
+#    interp.run('''if True:
+#        data = rch.recv()
+#        while data:
+#            handle_data(data)
+#            data = rch.recv()
+#        ''', channels={'rch': rch})
+#
+#t = Thread(target=handler)
+#t.start()
+#
+#sch.send(b'spam')
+#sch.send(b'eggs')
+#sch.send(b'')
+#
+#t.join()
+
+
+#############################
+
+section_header('example 6')
+
+"""
+>>> rch, sch = channels.create()
+>>> def handler():
+...     interp.run('''if True:
+...         handle_data( rch.recv() )
+...         ''', shared={'rch': rch})
+...
+>>> Thread(target=handler).start()
+>>> data = np.array([1, 2, 3])
+>>> sch.send(data)
+"""
+
+#rch, sch = interpreters.create_channel()
+#
+#def handler():
+#    interp.run('''if True:
+#        handle_data( rch.recv() )
+#        ''', shared={'rch': rch})
+#
+#Thread(target=handler).start()
+#data = np.array([1, 2, 3])
+#sch.send(data)

docs/subinterpreters/basic_executing.py

@@ -0,0 +1,91 @@
+import os
+import sys
+import subprocess
+from test.support import interpreters
+
+
+script = '''
+print('Hello world!')
+'''
+
+
+def section_header(label):
+    print()
+    print('####################')
+    print(f'# {label}')
+    print('####################')
+    print()
+
+
+#############################
+
+interp = interpreters.create()
+
+
+#############################
+
+section_header('example 1')
+
+"""
+>>> print('Hello world!')
+"""
+
+print('Hello world!')
+
+
+#############################
+
+section_header('example 2')
+
+"""
+$ python3 -c "
+print('Hello world!')
+"
+"""
+
+subprocess.run(f'{sys.executable} -c "{script}"', shell=True)
+
+
+#############################
+
+section_header('example 3')
+
+"""
+$ cat << EOF > hello.py
+print('Hello world!')
+EOF
+$ python3 hello.py
+"""
+
+with open('hello.py', 'w') as outfile:
+    outfile.write(script)
+subprocess.run(f'{sys.executable} hello.py', shell=True)
+os.unlink('hello.py')
+
+
+#############################
+
+section_header('example 4')
+
+"""
+>>> script = '''
+print('Hello world!')
+'''
+>>> exec(script)
+"""
+
+exec(script)
+
+
+#############################
+
+section_header('example 5')
+
+"""
+>>> script = '''
+print('Hello world!')
+'''
+>>> interp.run(script)
+"""
+
+interp.run(script)