homework-jianmu/2.0/src/connector/python

TDengine Connector for Python

TDengine connector for Python enables python programs to access TDengine, using an API which is compliant with the Python DB API 2.0 (PEP-249). It uses TDengine C client library for client server communications.

Install

git clone --depth 1 https://github.com/taosdata/TDengine.git
pip install ./TDengine/src/connector/python

Source Code

TDengine connector for Python source code is hosted on GitHub.

Examples

Query with PEP-249 API

import taos

conn = taos.connect()
cursor = conn.cursor()

cursor.execute("show databases")
results = cursor.fetchall()
for row in results:
    print(row)
cursor.close()
conn.close()

Query with objective API

import taos

conn = taos.connect()
conn.exec("create database if not exists pytest")

result = conn.query("show databases")
num_of_fields = result.field_count
for field in result.fields:
    print(field)
for row in result:
    print(row)
result.close()
conn.exec("drop database pytest")
conn.close()

Query with async API

from taos import *
from ctypes import *
import time

def fetch_callback(p_param, p_result, num_of_rows):
    print("fetched ", num_of_rows, "rows")
    p = cast(p_param, POINTER(Counter))
    result = TaosResult(p_result)

    if num_of_rows == 0:
        print("fetching completed")
        p.contents.done = True
        result.close()
        return
    if num_of_rows < 0:
        p.contents.done = True
        result.check_error(num_of_rows)
        result.close()
        return None
    
    for row in result.rows_iter(num_of_rows):
        # print(row)
        None
    p.contents.count += result.row_count
    result.fetch_rows_a(fetch_callback, p_param)
    


def query_callback(p_param, p_result, code):
    # type: (c_void_p, c_void_p, c_int) -> None
    if p_result == None:
        return
    result = TaosResult(p_result)
    if code == 0:
        result.fetch_rows_a(fetch_callback, p_param)
    result.check_error(code)


class Counter(Structure):
    _fields_ = [("count", c_int), ("done", c_bool)]

    def __str__(self):
        return "{ count: %d, done: %s }" % (self.count, self.done)


def test_query(conn):
    # type: (TaosConnection) -> None
    counter = Counter(count=0)
    conn.query_a("select * from log.log", query_callback, byref(counter))

    while not counter.done:
        print("wait query callback")
        time.sleep(1)
    print(counter)
    conn.close()


if __name__ == "__main__":
    test_query(connect())

Statement API - Bind row after row

from taos import *

conn = connect()

dbname = "pytest_taos_stmt"
conn.exec("drop database if exists %s" % dbname)
conn.exec("create database if not exists %s" % dbname)
conn.select_db(dbname)

conn.exec(
    "create table if not exists log(ts timestamp, bo bool, nil tinyint, \
        ti tinyint, si smallint, ii int, bi bigint, tu tinyint unsigned, \
        su smallint unsigned, iu int unsigned, bu bigint unsigned, \
        ff float, dd double, bb binary(100), nn nchar(100), tt timestamp)",
)

stmt = conn.statement("insert into log values(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)")

params = new_bind_params(16)
params[0].timestamp(1626861392589)
params[1].bool(True)
params[2].null()
params[3].tinyint(2)
params[4].smallint(3)
params[5].int(4)
params[6].bigint(5)
params[7].tinyint_unsigned(6)
params[8].smallint_unsigned(7)
params[9].int_unsigned(8)
params[10].bigint_unsigned(9)
params[11].float(10.1)
params[12].double(10.11)
params[13].binary("hello")
params[14].nchar("stmt")
params[15].timestamp(1626861392589)
stmt.bind_param(params)

params[0].timestamp(1626861392590)
params[15].null()
stmt.bind_param(params)
stmt.execute()


result = stmt.use_result()
assert result.affected_rows == 2
result.close()

result = conn.query("select * from log")

for row in result:
    print(row)
result.close()
stmt.close()
conn.close()

Statement API - Bind multi rows

from taos import *

conn = connect()

dbname = "pytest_taos_stmt"
conn.exec("drop database if exists %s" % dbname)
conn.exec("create database if not exists %s" % dbname)
conn.select_db(dbname)

conn.exec(
    "create table if not exists log(ts timestamp, bo bool, nil tinyint, \
        ti tinyint, si smallint, ii int, bi bigint, tu tinyint unsigned, \
        su smallint unsigned, iu int unsigned, bu bigint unsigned, \
        ff float, dd double, bb binary(100), nn nchar(100), tt timestamp)",
)

stmt = conn.statement("insert into log values(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)")

params = new_multi_binds(16)
params[0].timestamp((1626861392589, 1626861392590, 1626861392591))
params[1].bool((True, None, False))
params[2].tinyint([-128, -128, None]) # -128 is tinyint null
params[3].tinyint([0, 127, None])
params[4].smallint([3, None, 2])
params[5].int([3, 4, None])
params[6].bigint([3, 4, None])
params[7].tinyint_unsigned([3, 4, None])
params[8].smallint_unsigned([3, 4, None])
params[9].int_unsigned([3, 4, None])
params[10].bigint_unsigned([3, 4, None])
params[11].float([3, None, 1])
params[12].double([3, None, 1.2])
params[13].binary(["abc", "dddafadfadfadfadfa", None])
params[14].nchar(["涛思数据", None, "a long string with 中文字符"])
params[15].timestamp([None, None, 1626861392591])
stmt.bind_param_batch(params)
stmt.execute()


result = stmt.use_result()
assert result.affected_rows == 3
result.close()

result = conn.query("select * from log")
for row in result:
    print(row)
result.close()
stmt.close()
conn.close()

Statement API - Subscribe

import taos

conn = taos.connect()
dbname = "pytest_taos_subscribe_callback"
conn.exec("drop database if exists %s" % dbname)
conn.exec("create database if not exists %s" % dbname)
conn.select_db(dbname)
conn.exec("create table if not exists log(ts timestamp, n int)")
for i in range(10):
    conn.exec("insert into log values(now, %d)" % i)

sub = conn.subscribe(True, "test", "select * from log", 1000)
print("# consume from begin")
for ts, n in sub.consume():
    print(ts, n)

print("# consume new data")
for i in range(5):
    conn.exec("insert into log values(now, %d)(now+1s, %d)" % (i, i))
    result = sub.consume()
    for ts, n in result:
        print(ts, n)

print("# consume with a stop condition")
for i in range(10):
    conn.exec("insert into log values(now, %d)" % int(random() * 10))
    result = sub.consume()
    try:
        ts, n = next(result)
        print(ts, n)
        if n > 5:
            result.stop_query()
            print("## stopped")
            break
    except StopIteration:
        continue

sub.close()

conn.exec("drop database if exists %s" % dbname)
conn.close()

Statement API - Subscribe asynchronously with callback

from taos import *
from ctypes import *

import time


def subscribe_callback(p_sub, p_result, p_param, errno):
    # type: (c_void_p, c_void_p, c_void_p, c_int) -> None
    print("# fetch in callback")
    result = TaosResult(p_result)
    result.check_error(errno)
    for row in result.rows_iter():
        ts, n = row()
        print(ts, n)


def test_subscribe_callback(conn):
    # type: (TaosConnection) -> None
    dbname = "pytest_taos_subscribe_callback"
    try:
        conn.exec("drop database if exists %s" % dbname)
        conn.exec("create database if not exists %s" % dbname)
        conn.select_db(dbname)
        conn.exec("create table if not exists log(ts timestamp, n int)")

        print("# subscribe with callback")
        sub = conn.subscribe(False, "test", "select * from log", 1000, subscribe_callback)

        for i in range(10):
            conn.exec("insert into log values(now, %d)" % i)
            time.sleep(0.7)
        sub.close()

        conn.exec("drop database if exists %s" % dbname)
        conn.close()
    except Exception as err:
        conn.exec("drop database if exists %s" % dbname)
        conn.close()
        raise err


if __name__ == "__main__":
    test_subscribe_callback(connect())

Statement API - Stream

from taos import *
from ctypes import *

def stream_callback(p_param, p_result, p_row):
    # type: (c_void_p, c_void_p, c_void_p) -> None

    if p_result == None or p_row == None:
        return
    result = TaosResult(p_result)
    row = TaosRow(result, p_row)
    try:
        ts, count = row()
        p = cast(p_param, POINTER(Counter))
        p.contents.count += count
        print("[%s] inserted %d in 5s, total count: %d" % (ts.strftime("%Y-%m-%d %H:%M:%S"), count, p.contents.count))

    except Exception as err:
        print(err)
        raise err


class Counter(ctypes.Structure):
    _fields_ = [
        ("count", c_int),
    ]

    def __str__(self):
        return "%d" % self.count


def test_stream(conn):
    # type: (TaosConnection) -> None
    dbname = "pytest_taos_stream"
    try:
        conn.exec("drop database if exists %s" % dbname)
        conn.exec("create database if not exists %s" % dbname)
        conn.select_db(dbname)
        conn.exec("create table if not exists log(ts timestamp, n int)")

        result = conn.query("select count(*) from log interval(5s)")
        assert result.field_count == 2
        counter = Counter()
        counter.count = 0
        stream = conn.stream("select count(*) from log interval(5s)", stream_callback, param=byref(counter))

        for _ in range(0, 20):
            conn.exec("insert into log values(now,0)(now+1s, 1)(now + 2s, 2)")
            time.sleep(2)
        stream.close()
        conn.exec("drop database if exists %s" % dbname)
        conn.close()
    except Exception as err:
        conn.exec("drop database if exists %s" % dbname)
        conn.close()
        raise err


if __name__ == "__main__":
    test_stream(connect())

Insert with line protocol

import taos

conn = taos.connect()
dbname = "pytest_line"
conn.exec("drop database if exists %s" % dbname)
conn.exec("create database if not exists %s precision 'us'" % dbname)
conn.select_db(dbname)

lines = [
    'st,t1=3i64,t2=4f64,t3="t3" c1=3i64,c3=L"pass",c2=false,c4=4f64 1626006833639000000ns',
    'st,t1=4i64,t3="t4",t2=5f64,t4=5f64 c1=3i64,c3=L"pass it again",c2=true,c4=5f64,c5=5f64,c6=7u64 1626006933640000000ns',
    'stf,t1=4i64,t3="t4",t2=5f64,t4=5f64 c1=3i64,c3=L"pass it again_stf",c2=false,c5=5f64,c6=7u64 1626006933641000000ns',
]
conn.insert_lines(lines)
print("inserted")

lines = [
    'stf,t1=5i64,t3="t4",t2=5f64,t4=5f64 c1=3i64,c3=L"pass it again_stf",c2=false,c5=5f64,c6=7u64 1626006933641000000ns',
]
conn.insert_lines(lines)

result = conn.query("show tables")
for row in result:
    print(row)
result.close()


conn.exec("drop database if exists %s" % dbname)
conn.close()

License - AGPL-3.0

Keep same with TDengine.