taospy 2.2.3

TDengine connector for 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

You can use pip to install the connector from PyPI:

pip install taospy

Or with git url:

pip install git+https://github.com/taosdata/taos-connector-python.git

If you have installed TDengine server or client with pre-built packages, then you can install the connector from path:

pip install /usr/local/taos/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.execute("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.execute("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 is 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.execute("drop database if exists %s" % dbname)
conn.execute("create database if not exists %s" % dbname)
conn.select_db(dbname)

conn.execute(
    "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.execute("drop database if exists %s" % dbname)
conn.execute("create database if not exists %s" % dbname)
conn.select_db(dbname)

conn.execute(
    "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()

Subscription

import taos
import random

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

sub = conn.subscribe(False, "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.execute("insert into log values(now, %d)(now+1s, %d)" % (i, i))
    result = sub.consume()
    for ts, n in result:
        print(ts, n)

sub.close(True)
print("# keep progress consume")
sub = conn.subscribe(False, "test", "select * from log", 1000)
result = sub.consume()
rows = result.fetch_all()
# consume from latest subscription needs root privilege(for /var/lib/taos).
assert result.row_count == 0
print("## consumed ", len(rows), "rows")

print("# consume with a stop condition")
for i in range(10):
    conn.execute("insert into log values(now, %d)" % random.randint(0, 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()
# sub.close()

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

Subscription 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(c_void_p(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:
        print("drop if exists")
        conn.execute("drop database if exists %s" % dbname)
        print("create database")
        conn.execute("create database if not exists %s" % dbname)
        print("create table")
        # conn.execute("use %s" % dbname)
        conn.execute("create table if not exists %s.log(ts timestamp, n int)" % dbname)
        
        print("# subscribe with callback")
        sub = conn.subscribe(False, "test", "select * from %s.log" % dbname, 1000, subscribe_callback)
        
        for i in range(10):
            conn.execute("insert into %s.log values(now, %d)" % (dbname, i))
            time.sleep(0.7)
        
        sub.close()
        
        conn.execute("drop database if exists %s" % dbname)
        # conn.close()
    except Exception as err:
        conn.execute("drop database if exists %s" % dbname)
        # conn.close()
        raise err


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

Insert with line protocol

import taos
from taos import SmlProtocol, SmlPrecision

conn = taos.connect()
dbname = "pytest_line"
conn.execute("drop database if exists %s" % dbname)
conn.execute("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 1626006833639000000',
]
conn.schemaless_insert(lines, taos.SmlProtocol.LINE_PROTOCOL, taos.SmlPrecision.NOT_CONFIGURED)
print("inserted")

conn.schemaless_insert(lines, taos.SmlProtocol.LINE_PROTOCOL, taos.SmlPrecision.NOT_CONFIGURED)

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


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

License

We use MIT license for Python connector.