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I'm building a GameClient-Class in Python which handles user input and has to read from a database (MongoDb). I want to know if that is the best practice to implement it, so that I can use it with Python's with statement.

Because I want to use different functions of my Client class, __enter__ has to return self, so that I can use the instance of that class like normal. Is that best practice?

class Client(object):

    def __init__(self, playerid):
        self.MongoClient = MongoClient()
        self.db = self.MongoClient['worldbg-database']
        self.id = playerid

    def __exit__(self, exception_type, exception_val, trace):
        self.MongoClient.close()

    def __enter__(self):
        return self

    def handle_input(self, input):
    if input == "exit":
        return False


with Client("id") as GameClient:
    GameClient.select_my_tile(GameClient.get_my_tiles()[0]['_id'])
    while GameClient.handle_input(raw_input('command: ')):
        pass
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The reason to use a with clause is 1) clarity and 2) exception handling. Clarity because you have explicitly called out "right here, I am working with the object" and exception handling because you are guaranteed to have the exit handler called and any cleanup accomplished.

Canonical examples are:

with open(filename, "w") as fp:
    data = generate_some_data()
    fp.write(data)
    data2 = more_generation()
    fp.write(data2)

with lock:
    # all code in here is locked

You don't provide a lot of information about what you intend to accomplish in the with clause in your code. Typically the with block is not too long and focused on a task. If Client is meant to represent a player then you are probably putting the abstraction in the wrong place. A GameClient class could contain a DBConnection object. This way you could mock out the DB for testing for instance. Or switch to another DB type. If you meant Client to be DBClient I would rename it.

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  • \$\begingroup\$ I've edited my question to provide more information \$\endgroup\$ – Eknoes Jul 15 '14 at 16:00

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