PyDictDatabase

Introduction

PyDictDatabase is a Python Dictionary based database for tiny databases.

useful for

• matrix or very small database

• static database structure (more or less)

useless for

• collecting data

• growing databases

comment:

I am using this type of database in two of my projects:

1. for my plant watering system to collect my last status data

2. for my SmartPi as manageable & clear structure for matrixes

The SmartPi also uses a MySQL database to collect data. As there are many read/write cycles for some attributes. It makes more sense to leave them in memory which is also gentler on the memory card (Raspberry Pi).

Features

• use SELECT and UPDATE like MySQL

• existing data types are retained

• SELECT methods: fetchone & fetchall

• UPDATE methods: commit

• optional: export the last status data to a file and reload it during initialization

Usage example

You have to save the file PyDictDatabase.py in your project directory.

setup database

from PyDictDatabase import *

data = {
        'table1':  {
                    1: {'id':1,'key':"value"},
                    2: {'id':2,'key':"value"},
                    },
        'table2':  {
                    1: {'id':1,'name':"name1",'status':True},
                    2: {'id':2,'name':"name2",'status':False},
                    },
       }

DictDB = PyDictDatabase(database=data)

use options

DictDB = PyDictDatabase(database=data,settings={"ERROR_OUTPUT":True})

options:

• "EXPORT_DATABASE":True for export the last status data to a file and reload it during initialization (default: False)
• "ERROR_OUTPUT":True for error output, DEBUG-MODE (default: False)
• "ERROR_EXIT":True to stop script with exit(1), if an error occurs with select/update (default: False)

SELECT Data (short instruction)

result = DictDB.fetchone("SELECT status FROM table2 WHERE id = name1")
result = DictDB.fetchall("SELECT id,status FROM table2 WHERE id = name1")

UPDATE Data (short instruction)

result = DictDB.commit("UPDATE table2 SET status = False WHERE id = name1")

Rules

• dict must start with 1, instead of 0

• use the same keys per table (so it is also common with MySQL)

Return codes

fetchone / fetchall (SELECT)

None - no entry found

commit (UPDATE)

20 SUCCESS - nothing amiss

40 ERROR - for further information activate ERROR_OUTPUT

44 NOT FOUND - name of the table/key not found

Syntax

SYNTAX fetchone:

SELECT `KEY` FROM `TABLE` WHERE `KEY` = `VALUE`

SYNTAX fetchall:

SELECT `KEY` FROM `TABLE` WHERE `KEY` = `VALUE`

SELECT `KEY`,`KEY`,`KEY` FROM `TABLE` WHERE `KEY` = `VALUE`

SYNTAX commit:

UPDATE `TABLE` SET `KEY` = `VALUE` WHERE `KEY` = `VALUE`

UPDATE `TABLE` SET `KEY` = `VALUE`,`KEY` = `VALUE`,`KEY` = `VALUE` WHERE `KEY` = `VALUE`

in progress

• implement a findall method for chaining

• INSERT option to add a new entry

Changelog

v1.1.0 (09.05.2020)

• new feature: Export-Database

v1.0.0 (04.05.2020)

• initial release