学习来源：https://github.com/dgraph-io/pydgraph
dgraph说明文档https://dgraph.io/docs/get-started/

安装pydgraph

pip install pydgraph

官方文档说明，为了避免在添加复合凭据或使用客户端授权时出现问题，请安装gRPC 1.19.0版本:

pip install grpcio==1.19.0

我直接pip install grpcio了，没设置版本
安装完成后在自己的环境中验证一下是否安装成功

import pydgraph
pydgraph.VERSION

连接到dgraph

链接dgraph之前先启动zero和alpha，ratel可以做实验的时候查看效果用
启动之后创建client_stub和client，类似py2neo里的Graph连接到neo4j

client_stub = pydgraph.DgraphClientStub('localhost:9080')
client = pydgraph.DgraphClient(client_stub)

删除dgraph中所有数据

client.alter(pydgraph.Operation(drop_all=True))

创建SCHEMA

schema = """
    name: string @index(exact) .
    friend: [uid] @reverse .
    age: int .
    married: bool .
    loc: geo .
    dob: datetime .
    type Person {
        name
        friend
        age
        married
        loc
        dob
    }
    """
client.alter(pydgraph.Operation(schema=schema))

这里的schema和dgraph中编辑的schema是相同格式的（注意三引号，否则报错）

Edit Schema File

用rdf格式创建数据

后几行()小括号里面的是边属性，不可设置中文

txbb = '''
<_:person001> <name> "丁丁" .
<_:person001> <'颜色'> "紫色" .
<_:person001> <antenna_shape> "三角形" .
<_:person001> <height> "304" .
<_:person002> <name> "迪西" .
<_:person002> <color> "绿色" .
<_:person002> <antenna_shape> "直线形" .
<_:person002> <height> "259" .
<_:person003> <name> "拉拉" .
<_:person003> <color> "黄色" .
<_:person003> <antenna_shape> "螺旋" .
<_:person002> <height> "245" .
<_:person004> <name> "小波" .
<_:person004> <color> "红色" .
<_:person004> <antenna_shape> "圆形" .
<_:person004> <height> "182" .
<_:person001> <'朋友'> <_:person002> (friendship=1.0) . 
<_:person001> <friend> <_:person003> (friendship=0.9) . 
<_:person001> <friend> <_:person004> (friendship=0.8) . 
<_:person002> <friend> <_:person003> . 
<_:person002> <friend> <_:person004> . 
<_:person003> <friend> <_:person004> . 
'''
txn = client.txn()
txn.mutate(set_nquads=txbb)
txn.commit()

用json格式创建数据

def create_data(client):
    # Create a new transaction.
    txn = client.txn()
    try:
        # Create data.
        p = {
            'uid': '_:alice',
            'dgraph.type': 'Person',
            'name': 'Alice',
            'age': 26,
            'married': True,
            'loc': {
                'type': 'Point',
                'coordinates': [1.1, 2],
            },
            'dob': datetime.datetime(1980, 1, 1, 23, 0, 0, 0).isoformat(),
            'friend': [
                {
                    'uid': '_:bob',
                    'dgraph.type': 'Person',
                    'name': 'Bob',
                    'age': 24,
                }
            ],
            'school': [
                {
                    'name': 'Crown Public School',
                }
            ]
        }

        # Run mutation.
        response = txn.mutate(set_obj=p)

        # Commit transaction.
        txn.commit()

        # Get uid of the outermost object (person named "Alice").
        # response.uids returns a map from blank node names to uids.
        print('Created person named "Alice" with uid = {}'.format(response.uids['alice']))

    finally:
        # Clean up. Calling this after txn.commit() is a no-op and hence safe.
        txn.discard()

边属性在json中设置格式：（例如上例中friend关系）

'friend': [
                {
                    'uid': '_:bob',
                    'dgraph.type': 'Person',
                    'name': 'Bob',
                    'age': 24,
                    'friend|boyfriend': True,
                }
            ],

删除数据

def delete_data(client):
    # Create a new transaction.
    txn = client.txn()
    try:
        query1 = """query all($a: string) {
            all(func: eq(name, $a)) {
               uid
            }
        }"""
        variables1 = {'$a': 'Bob'}
        res1 = client.txn(read_only=True).query(query1, variables=variables1)
        ppl1 = json.loads(res1.json)
        for person in ppl1['all']:
            print("Bob's UID: " + person['uid'])
            txn.mutate(del_obj=person)
            print('Bob deleted')
        txn.commit()

    finally:
        txn.discard()

查询数据

数据以字典的格式返回

def query_alice(client):
    # Run query.
    query = """query all($a: string) {
        all(func: eq(name, $a)) {
            uid
            name
            age
            married
            loc
            dob
            friend {
                name
                age
            }
            school {
                name
            }
        }
    }"""

    variables = {'$a': 'Alice'}
    res = client.txn(read_only=True).query(query, variables=variables)
    ppl = json.loads(res.json)

    # Print results.
    print('Number of people named "Alice": {}'.format(len(ppl['all'])))
    return ppl

查询并添加数据

query = """{
  u as var(func: eq(name, "Alice"))
}"""
nquad = """
  uid(u) <name> "Alice" .
  uid(u) <age> "25" .
  <_:tom> <name> "Tom" .
  uid(u) <boyfriend> <_:tom> (love=1) .
"""
txn = client.txn()
mutation = txn.create_mutation(set_nquads=nquad)
request = txn.create_request(query=query, mutations=[mutation], commit_now=True)
txn.do_request(request)