You should invoke self.connection.close
in your Device.close()
method, and then arrange for that to be invoked properly in your program, perhaps with a context manager.
__del__
is never worth it.
Question
How would I use a Contextmanager for instance variables? E.g.
Let's assume I've got some Connection
class, that must be closed on destruction. If I were to implement it as a ContextManager I could do.
with Connection() as c:
c.write('FOO')
c.ask('BAR?')
and it would get automatically closed on destruction. But what if I wanted to use it in a __init__
of another class, e.g. like the following example?
class Device(object):
def __init__(self):
self.connection = Connection() # Must be closed on destruction.
I dont want it to be closed on exit of the constructor, it should die when the object get's destroyed. I could use __del__
but this has it's downsides. Being used to RAII in C++ it baffles me.
So what is the best way to do it in this case?
Solution
You should invoke self.connection.close
in your Device.close()
method, and then arrange for that to be invoked properly in your program, perhaps with a context manager.
__del__
is never worth it.
OTHER TIPS
from contextlib import contextmanager
@contextmanager
def connection():
conn = Conn()
try:
yield conn
finally:
conn.close()
class Conn(object):
def close(self):
print('Closing')
class Device(object):
def __init__(self, conn):
self.conn = Conn()
with connection() as conn:
d = Device(conn)