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Version: 2.4.x

Python

With the release of the new version of distributed, attentive friends must have noticed that CnosDB 2.0 now fully supports Python.By calling the connector cnos-connector, the connection between CnosDB 2.0 and Python is achieved.The cnos-connector encapsulated requests for CnosDB to make the use of CnosDB in Python environment more concise and user-friendly.At the same time, cnos-connector provides a programming interface that complies with PEP 249, making it easier to interact with SQLAlchemy and pandas.

cnos-connector is fully open source and the source code is located on GitHub.

Install​

Download and install cnos-connector using pip, which requires Python version greater than or equal to 3.6

pip install cnos-connector

Usage Examples​

Query example​

  • Query by SQL​

    from cnosdb_connector import connect

    conn = connect(url="http://127.0.0.1:8902/", user="root", password="")
    resp = conn.execute("SHOW DATABASES")
    print(resp)

  • Query by function defined by the interface​

    from cnosdb_connector import connect

    conn = connect(url="http://127.0.0.1:8902/", user="root", password="")
    conn.create_database("air")
    resp = conn.list_database()
    print(resp)

  • Search through PEP-249, for more information, please refer to PEP-249.​

    from cnosdb_connector import connect

    conn = connect(url="http://127.0.0.1:8902/", user="root", password="")
    cursor = conn.cursor()

    cursor.execute("SHOW DATABASES")
    resp = cursor.fetchall()
    print(resp)

  • Querying via pandas, which supports the PEP-249 specification​

    import pandas as pd
    from cnosdb_connector import connect

    conn = connect(url="http://127.0.0.1:8902/", user="root", password="")

    resp = pd.read_sql("SHOW DATABASES", conn)
    print(resp)

Writing example​

  • supports the Line Protocol method for writing data.​

    from cnosdb_connector import connect

    line0 = "air,station=XiaoMaiDao temperature=56,pressure=77 1666165200290401000"
    line1 = "air,station=XiaoMaiDao temperature=72,pressure=71 1666165300290401000"
    line2 = "air,station=XiaoMaiDao temperature=46,pressure=67 1666165400290401000"

    conn = connect(url="http://127.0.0.1:8902/", user="root", password="")

    conn.create_database_with_ttl("ocean", "100000d")
    conn.switch_database("ocean")

    conn.write_lines([line0, line1, line2])

    resp = conn.execute("SELECT * FROM ocean;")
    print(resp)

  • Support SQL for writing​

    from cnosdb_connector import connect

    conn = connect(url="http://127.0.0.1:8902/", user="root", password="")

    query = "INSERT INTO air (TIME, station, visibility, temperature, pressure) VALUES
                    (1666165200290401000, 'XiaoMaiDao', 56, 69, 77); "

    conn.execute(query)

    resp = conn.execute("SELECT * FROM ocean;")
    print(resp)

  • Support for writing in CSV format​

    from cnosdb_connector import connect
    import os

    query = "CREATE TABLE air (\
                 visibility DOUBLE,\
                 temperature DOUBLE,\
                 pressure DOUBLE,\
                 TAGS(station));"

    conn = connect(url="http://127.0.0.1:8902/", user="root", password="")
    # table schema must same with csv file
    conn.execute(query)

    path = os.path.abspath("test.csv")
    conn.write_csv("air", path)

    resp = conn.execute("SELECT * FROM air;")
    print(resp)

Interface Documentation​

In order to make it easier for users to connect to CnosDB, cnosdb_connector provides a simple wrapper for some common SQL.

# CREATE DATABASE database_name;
def create_database(self, database_name)

# CREATE DATABASE database_name WITH TTL ttl;
def create_database_with_ttl(self, database_name, ttl)

# CREATE USER user WITH PASSWORD = password;
def create_user(self, user, password)

# DROP DATABASE database_name;
def drop_database(self, database_name)

# DROP TABLE table_name;
def drop_table(self, table_name)

# DROP USER user;
def drop_user(self, user)

# SHOW DATABASES;
def list_database(self)

# SHOW TABLES;
def list_table(self)

If you have a better idea for an interface wrapper, feel free to submit a PR to our Python Connector source code repository.