Check if document exists using cloudant-2.0.0b2 in IBM Bluemix and Python - python-2.7

Question

I am using:
A Python application in Bluemix
Bluemix cloudant v2.0.0b2 database linked to the Python app
According to https://pypi.python.org/pypi/cloudant/2.0.0b2, everything broke from 0.5 to 2.0, and they are still working on the documentation as everything is Beta. Next to this, I am also new to Python and databases. Documentation can be found here:
http://python-cloudant.readthedocs.io/en/latest/getting_started.html
What I am trying to do is check if a document already exists.
Things that I have tried:
from cloudant.account import Cloudant
import time
import json
# Connect to the database
client = Cloudant(*hidden*)
client.connect()
# The database we work in
db = client['myDatabase']
# The document we work on
doc = db['myDocument']
print doc.exists()
But the code fails before retrieving the document. I checked the source code, and it looks like it is supposed to:
def __getitem__(self, key):
if key in list(self.keys()):
return super(CouchDatabase, self).__getitem__(key)
if key.startswith('_design/'):
doc = DesignDocument(self, key)
else:
doc = Document(self, key)
if doc.exists():
doc.fetch()
super(CouchDatabase, self).__setitem__(key, doc)
return doc
else:
raise KeyError(key)
Source: https://pypi.python.org/pypi/cloudant/2.0.0b2
Is there a way I can check if the document exists before I retrieve it? Or should I retrieve it and catch the error? Or is there a different approach?

Answer 1

The behavior you are describing is the desired behavior for the python-cloudant library database object, so if you intend to use the database object to retrieve your documents and populate your local database cache you should look to except a KeyError in the event of a non-existent document and handle accordingly. However, if are interested in capturing whether a document exists before bringing it into your local database cache then changing your code to something like:
from cloudant.account import Cloudant
from cloudant.document import Document
# Connect to the database
client = Cloudant(*hidden*)
client.connect()
# The database we work in
db = client['myDatabase']
# The document we work on
if Document(db, 'myDocument').exists():
doc = db['myDocument']
would do the trick.
Similarly you could just do:
from cloudant.account import Cloudant
from cloudant.document import Document
# Connect to the database
client = Cloudant(*hidden*)
client.connect()
# The database we work in
db = client['myDatabase']
# The document we work on
doc = Document(db, 'myDocument')
if doc.exists():
doc.fetch()
But this would not populate your local database cache, the db dictionary.