SQLite in Python Tutorial

In this tutorial, we will discuss how to connect to an existing SQLite database, creating a new SQLite database, and manipulating SQLite tables all using Python.  I will assume you already have and understand Python and SQLite.  If not, the official Python documentation is a good place to start learning Python and my introduction to SQLite should be enough for you to understand this tutorial.

Connect to an Existing SQLite Database

In order to connect to SQLite, we will need to use the built in sqlite3 module and create a connection variable.

[python]

import sqlite3
conn = sqlite3.connect(‘C:\\Users\\Allison\\pantrydb.db’)
c = conn.cursor()

[/python]

Create a New SQLite Database

Creating a new SQLite database is quite simple.  If the database you are trying to connect to doesn’t already exist, SQLite will create it for us.

[python]

import sqlite3
conn = sqlite3.connect(‘testdb.sqlite’)
c = conn.cursor()

[/python]

Create a New Table

Next, we will create a table with one column:

[python]

c.execute(‘CREATE TABLE customer (customer_id INTEGER PRIMARY KEY AUTOINCREMENT,
firstname VARCHAR(50) NOT NULL)’)

conn.commit()

conn.close()

[/python]

Lets make sure this worked.  Open the command prompt (windows key + r) and type ‘cmd’.  Next, type

[text]

sqlite3 pantrydb.db

[/text]

This will open your SQLite database.  Next, to see if the table was created, type:

[text]

.tables

[/text]

The ‘customer’ table should be listed below.  To make sure it is correct, check the schema by typing:

[text]

.schema customer

[/text]

Add a New Column with Variables

First, lets define our variables:

[python]

database = ‘pantrydb.db’
table = ‘customer’
id_column = ‘customer_id’ # name of the PRIMARY KEY column
newcolumn = ‘lastname’
column_type = ‘VARCHAR(50)’

[/python]

Next, we will connect to the database and execute the ALTER TABLE statement.  To do this without a default value (default = NULL):

[python]

conn = sqlite3.connect(database)
c = conn.cursor()

c.execute(“ALTER TABLE {tn} ADD COLUMN ‘{cn}’ {ct}”\
.format(tn=table, cn=newcolumn, ct=column_type))

[/python]

To create a default value:

[python]

default_val = ‘Smith’
conn = sqlite3.connect(database)
c = conn.cursor()

c.execute(“ALTER TABLE {tn} ADD COLUMN ‘{cn}’ {ct} DEFAULT ‘{df}'”\
.format(tn=table, cn=newcolumn, ct=column_type, df=default_val))

conn.commit()
conn.close()

[/python]

Manipulating Rows

Manipulating rows follows the same formula as above.

[python]

database = ‘pantrydb.db’
table = ‘customer’
id_column = ‘customer_id’
column = ‘firstname’

conn = sqlite3.connect(database)
c = conn.cursor()

try:
c.execute(“INSERT INTO {tn} ({idf}, {cn}) VALUES (NULL, ‘Allison’)”.\
format(tn=table, idf=id_column, cn=column))
except sqlite3.IntegrityError:
print(‘ERROR: ID already exists in PRIMARY KEY column {}’.format(id_column))

conn.commit()
conn.close()

[/python]

 

That is the bulk of using Python with SQLite!  This should be enough foundation for you to be able to more or less manipulate a SQLite database with Python!  If you have any questions or comments, feel free to let me know below or contact me.

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