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    <p>So, syntax wise you have a number of problems. It looks like you're mixing a couple of tutorials in different ways. So, firstly I'll explain what is going on with your code and explain why you're seeing what you're seeing:</p> <pre><code>import pymongo class mongoDB(): # you don't need ()'s here - only if you are inheriting classes # you could inherit from object here, which is a good practice # by doing class mongoDb(object):, otherwise you can just take # them out conn = object # here, you're defining a class member - global for all instances # generally, you don't instantiate an object pointer like this, # you would set it to None instead. It won't fail doing this, # but it's not "right" def __init__(self): # the __init__ method is the constructor method - this will # allow you to initialize a particular instance of your class, represented # by the self argument. This method is called when you call the class, i.e. # inst = mongoDb() # in this case, the conn variable is not a global. Globals are defined # at the root module level - so in this example, only pymongo is a global # conn is a class member, and would be accessed by doing mongoDB.conn global conn # with that being said, you're initializing a local variable here called conn # that is not being stored anywhere - when this method finishes, this variable # will be cleaned up from memory, what you are thinking you're doing here # should be written as mongoDB.conn = pymongo.Connection("localhost", 27017) conn = pymongo.Connection("localhost",27017) def CreateCollection(name =""): # there is one of two things you are trying to do here - 1, access a class # level member called conn, or 2, access an instance member called conn # depending on what you are going for, there are a couple of different ways # to address it. # all methods for a class, by default, are instance methods - and all of them # need to take self as the first argument. An instance method of a class # will always be called with the instance first. Your error is caused because # you should declare the method as: # def CreateCollection(self, name = ""): # The alternative, is to define this method as a static method of the class - # which does not take an instance but applies to all instances of the class # to do that, you would add a @staticmethod decorator before the method. # either way, you're attempting to access the global variable "conn" here, # which again does not exist # the second problem with this, is that you are trying to take your variable # argument (name) and use it as a property. What python is doing here, is # looking for a member variable called name from the conn object. What you # are really trying to do is create a collection on the connection with the # inputed name # the pymongo class provides access to your collections via this method as a # convenience around the method, create_collection. In the case where you # are using a variable to create the collection, you would call this by doing # conn.create_collection(name) # but again, that assumes conn is what you think it is, which it isn't dbCollection = conn.name return dbCollection if __name__ == '__main__': # here you are just creating a pointer to your class, not instantiating it # you are looking for: # database = mongoDB() database = mongoDB # this is your error, because of the afore mentioned lack of 'self' argument collection = database.CreateCollection("Hello") </code></pre> <p>I'd say have a look through the Pep-8 (http://www.python.org/dev/peps/pep-0008/) coding style guides (very helpful) to learn about how to make your code "flow" pythonically.</p> <p>Having gone through your code to explain what is going on - this is what you are ultimately trying to do:</p> <pre><code>import pymongo class MongoDB: # Classes generally are camel-case, starting with uppercase def __init__(self, dbname): # the __init__ method is the class constructor, where you define # instance members. We'll make conn an instance member rather # than a class level member self._conn = pymongo.Connection("localhost", 27017) self._db = self._conn[dbname] # methods usually start with lowercase, and are either camel case (less desirable # by Python standards) or underscored (more desirable) # All instance methods require the 1st argument to be self (pointer to the # instance being affected) def createCollection(self, name=""): return self._db[name] if __name__ == '__main__': # you want to initialize the class database = MongoDB("Hello") collection = database.createCollection("MyTable") </code></pre> <p>Given that tho - what is the goal of writing this class wrapper? The same could be written as:</p> <pre><code>import pymongo conn = pymongo.Connection('localhost', 27017) database = conn["Hello"] collection = database["MyTable"] </code></pre> <p>If you're trying to create a larger API wrapped around the pymongo database, then I'd recommend looking into some ORM modules that have already been built. There are some out there - not 100% sure which ones are available for MongoDB, but the one I use (I am biased, I wrote it) is called ORB, and can be found at <a href="http://docs.projexsoftware.com/api/orb">http://docs.projexsoftware.com/api/orb</a></p>
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    1. USEric Hulser
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    1. COVery Informative sir. Thank you
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      1. USRob Schneider
    2. COYour code is exactly what I want to do and it looks right but when I run it i get the same error: unbound method createCollection() must be called with MongoDB instance as first argument (got str instance instead)
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      1. USRob Schneider
    3. COAre you using the first or second example? The first example is still broken...the second example SHOULD work...could you paste exactly what you have?
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