marians/CouchDB_Python.md

## CouchDB_Python.md

      
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              CouchDB_Python.md
            
          
    This is an unofficial manual for the couchdb Python module I wish I had had.
Installation

pip install couchdb

Importing the module

import couchdb
Connection

If you only need read access, use an anonymous connection:
couchserver = couchdb.Server("http://couchdb:5984/")
To write to the database, create an authenticated connection:
user = "admin"
password = "my secret password"
couchserver = couchdb.Server("http://%s:%s@couchdb:5984/" % (user, password))
Listing databases

Simply iterate over the server object like this:
for dbname in couchserver:
    print(dbname)
Selecting/creating a database to work with

dbname = "mydb"
if dbname in couchserver:
    db = couchserver[dbname]
else:
    db = couchserver.create(dbname)
Deleting a database

del couchserver[dbname]
Writing a document to a database

Storing a document with an auto-generated ID:
doc_id, doc_rev = db.save({'key': 'value'})
doc_id is the generated document ID, doc_rev is the revision identifier.
Setting a specific ID:
db["my_document_id"] = {'key': 'value'}
Writing multiple documents in one call is done via the update() method of the database object. This can either create new documents (when no _id field is present per document) or update existing ones.
docs = [{'key': 'value1'}, {'key': 'value2'}]
for (success, doc_id, revision_or_exception) in db.update(docs):
    print(success, docid, revision_or_exception)
Retrieving documents by ID

doc_id = "my_document_id"
doc = db[doc_id]  # or db.get(doc_id)
Querying documents from views

If your database has a design document and view under the path /db_name/_design/design_doc/_view/view_name, you can iterate this view using this syntax:
for item in db.view('design_doc/view_name'):
    print(item.key, item.id, item.value)
Limiting the output to a certain number of items:
for item in db.view('design_doc/view_name', limit=100):
    print(item.key, item.id, item.value)
Skipping the first n items:
for item in db.view('design_doc/view_name', skip=100):
    print(item.key, item.id, item.value)
Reverse sorting:
for item in db.view('design_doc/view_name', descending=True):
    print(item.key, item.id, item.value)
Including source documents in result entries:
for item in db.view('design_doc/view_name', include_docs=True):
    print(item.key, item.id, item.value)
Allow outdated data to be returned, prevent updating the view before returning results:
for item in db.view('design_doc/view_name', stale="ok"):
    print(item.key, item.id, item.value)
Update the view after returning the results:
for item in db.view('design_doc/view_name', stale="update_after"):
    print(item.key, item.id, item.value)
Grouping results

Grouping the results by key, using the Reduce function, must be activated explicitly:
for item in db.view('design_doc/view_name', group=True):
    print(item.key, item.value)
If the Map function emits a structured key (an array with multiple elements), the grouping level can be determined:
for item in db.view('design_doc/view_name', group=True, group_level=1):
    print(item.key, item.value)
Filtering

Return only entries from the view matching a certain key:
for item in db.view('design_doc/view_name', key="my_key"):
    print(item.key, item.id, item.value)
Return entries with keys in a certain range:
for item in db.view('design_doc/view_name', startkey="startkey", endkey="endkey"):
    print(item.key, item.id, item.value)
The key, startkey and endkey parameters also accept arrays, e. g.
for item in db.view('design_doc/view_name', startkey=["foo", "a"], endkey=["foo", "z"]):
    print(item.key, item.id, item.value)