Couchbase III(Python Library)

Couchbase III(Python Library)

第一步

安装

使用pip安装：

>pip install couchbase --quiet

确认是否安装成功：

>python -c "import couchbase"

API 第一印象

from couchbase import Couchbase
from couchbase.exceptions import CouchbaseError

c = Couchbase.connect(bucket='beer-sample', host='localhost')

try:
    beer = c.get("aass_brewery-juleol")

except CouchbaseError as e:
    print "Couldn't retrieve value for key", e
    # Rethrow the exception, making the application exit
    raise

doc = beer.value

# Because Python 2.x will complain if an ASCII format string is used
# with Unicode format values, we make the format string unicode as well.

print unicode("{name}, ABV: {abv}").format(name=doc['name'], abv=doc['abv'])

doc['comment'] = "Random beer from Norway"

try:
    result = c.replace("aass_brewery-juleol", doc)
    print result

except CouchbaseError as e:
    print "Couldn't replace key"
    raise

存储文档

基本操作

• set(key, value)

  Stores the document value under the key.
  If the key did not previously exist, it is created.
  If the key already exists, its existing value is overwritten with the new contents of value.
  

• add(key, value)

  Stores the document value under the key, but only if key does not already exist.
  If key already exists, an exception is thrown.
  

• replace(key, value)

  Replace is the inverse of add.
  It sets the contents of key to value, but only if the key already exists.
  If the key does not already exist, an exception is thrown.
  

• delete(key)

  Deletes the key from the bucket.
  Future attempts to access this key via get raise an exception until something is stored again
  for this key using one of the set methods.
  

获取文档

获取单文档

#无异常处理
client.store("my list", [])
result = client.get("my list")
doc = result.value

#异常处理版， 单请求
result = client.get("non-exist-key", quiet=True)
if result.success:
    print "Got document OK"
else:
    print ("Couldn't retrieve document. "
       "Result was received with code"), result.rc

#异常处理版，所有连接请求
client = Couchbase.connect(bucket='default', quiet=True)
result = client.get("non-exist-key")
if result.success:
    print "Got document OK"
else:
    print "Couldn't retrieve document"

获取多文档

client.set_multi({
    'sheep_counting' : ['first sheep', 'second sheep'],
    'famous_sheep' : {'sherry lewis' : 'Lamb Chop'}
})
keys = ('sheep_counting', 'famous_sheep')
results = client.get_multi(keys)
for key, result in results.items():
    doc = result.value

#异常处理版
results = client.get_multi(("i exist", "but i don't"), quiet=True)
#迭代判断
for key results:
if result.success:
    print "Got document OK"
    doc = result.value
else:
    print "Couldn't retrieve document"
#一次判断所有
#if not results.all_ok:
#print "Couldn't get all keys"

异常处理

文档不存在时 ，抛出 couchbase.exceptions.NotFoundError

使用 Connection.quiet 可以改变异常处理的行为

获取View

results = client.query("beer", "brewery_beers",
                   include_docs=True, limit=5)
for result in results:
    print "key is %r" % (result.key)
    doc = result.doc.value
    if doc['type'] == "beer":
        print "Got a beer. It's got %0.2f ABV" % (doc['abv'],)

• include_docs

  This boolean parameter indicates whether the corresponding document should be retrieved
  for each row fetched.
  If this is true, the doc property of the ViewRow object yielded by the iterator returned
  by query contains a Result object that contains the document for the key.
  

• reduce

  This boolean parameter indicates whether the server should also pass the results to
  the view’s reduce function.
  An exception is raised if the view does not have a reduce method defined.
  

• limit

  This numeric parameter indicates the maximum amount of results to fetch from the query.
  This parameter is handy if your query can produce a lot of results.
  

• descending

  This boolean parameter indicates that the results should be returned in reverse order.
  

• stale

  This boolean parameter controls the tradeoff between performance and freshness of data.
  

• debug

  This boolean parameter fetches low-level debugging information from the view engine.
  

• streaming

  This boolean parameter indicates whether the view results should be decoded in a streaming manner.
  When enabled, the iterator internally fetches chunks of the response as required.
  As this is less efficient than fetching all results at once, it is disabled by default,
  but can be very useful if you have a large dataset because
  it prevents the entire view from being buffered in memory.
  

编码与序列化

Python SDK 默认使用 编码格式JSON，使用json标准库

也可以指定使用其他编码格式：

import pprint
from couchbase import Couchbase, FMT_PICKLE
c = Couchbase.connect(bucket='default')
c.set("a_python_object", object(), format=FMT_PICKLE)
c.set("a_python_set", set([1,2,3]), format=FMT_PICKLE)
pprint.pprint(c.get("a_python_object").value)
pprint.pprint(c.get("a_python_set").value)

Output：

<object object at 0x7fa7d0ad80e0>
set([1, 2, 3])

链接

• Couchbase Python Client Library Documentation

• Couchbase Client Library: Python 1.0