Two python(3) classes with the same input (extending a python class) - python-3.x

Question

I have a design change I have been trying to implement with little success, as I can't seem to find my question anywhere.
Currently I have a python class that creates a database connection, stores the index name (table), and other attributes (specifically its an Elasticsearch database connection but that shouldn't matter for this question).
class Create:
# Functions to manipulate Index Objects
def __init__(self, index, type, host, shards=3, replicas=1):
# Create Index Object (OcrBook or OcrPage)
self.index = index
self.type = type
self.shards = shards
self.replicas = replicas
self.es_connection = Elasticsearch([{'host': host, 'port': 9200}])
Associated with this class are functions to manipulate the index objects, for example creating that index (table) on the database (cluster) or modifying that table in some way.
def create_index(self):
# Creates/Executes Index
try:
self.es_connection.indices.create(
index=self.index,
body={
'settings' : {
'number_of_shards' : self.shards,
'number_of_replicas': self.replicas,
}
})
except Exception:
CreateLog.write_log(Exception, 'Create Index Exception')
These being in the same class make sense to me, as the connection to the table/database and creating or modifying that table/database are connected to each other.
I also have a group of other functions that search that particular table. These I believe should be in a separate class as rather then creating or modifying the table/database they are simply searching the table/database and could ideally take any table/database initialized by the create class. Currently I tried breaking them up by doing the following:
class Search(Create):
def find_book(self, bookkey):
""" Finds a Book """
try:
results = self.es_connection.search(self.index, self.type, body={
"query": {
"match": {
"BookKey": bookkey
}
}
})
return results['hits']['hits']
except Exception:
CreateLog.write_log(Exception, 'Could Not Find Book')
This works on windows, but is not portable to 'linux' as the 'class has not been initialized' when I try to use the Search functionality. I know there is a design problem here, and I could combine both classes into one to fix the problem. But I would like to keep them separate. Is there a better way to 'inherit' (I don't believe that's the right word in this case) the object created in the 'Create' class by the search class, does anyone have a better way to separate these logically, or is there a better way to extend the create class with the search functionality? All input is helpful! Thank you.

Answer 1

You seem to be on a OOP path, but why exactly does Search has to be a class? You have a perfect task for a stand-alone function find_book(index_object, bookkey). It does not store anything internally, I do no see why this has to de a class, not a function.
Class naming can also be hinting at your design decisions (or problems). Class name is ususlly a noun, function name tends to be a verb. Create is not a perfect class name to me.
In your setting I'd go with a class IndexObjects (that is Create renamed) and function find_book(index_object, bookkey). You can switch to more of OOP once this design up and running.
Another split of responsibilities that comes to mind is below. Here you inject, not inherit, which allows you to parts more independent.
class IndexObject:
# ...
def query(self, query_dict):
return self.es_connection.search(self.index, self.type, body=query_dict)
class BookSearcher():
def __init__(self, index_object):
self.index_object = index_object
def find(self, book_key):
""" Finds a Book """
query_dict = {"query": {
"match": {
"BookKey": book_key
}
}
}
try:
results = self.index_object.query(query_dict)
return results['hits']['hits']
# FIXME: looks lile bare exception, not great
except Exception:
CreateLog.write_log(Exception, 'Could Not Find Book')