Develop Reference

Storing information in a file, Python

I'm making a car rental console base program in Python where I need to save data about cars I store (such as brand, registration number etc).
What would be the ideal type of file for such a thing, and how to iniciate it?

You can use sqlite3 to store the information.
You can create a table with columns such as brand,registration number etc.
If the registration number is unique to single type of car you can also take care of that condition in sqlite3
syntax is as simple as:
For creating table:
import sqlite3
conn = sqlite3.connect('test.db')
print "Opened database successfully";
conn.execute('''CREATE TABLE COMPANY
(REGISTRATION_NO INT PRIMARY KEY NOT NULL,
BRAND TEXT NOT NULL
);''')
print "Table created successfully";
conn.close()
For insertion:
import sqlite3
conn = sqlite3.connect('test.db')
print "Opened database successfully";
conn.execute("INSERT INTO COMPANY (REGISTRATION_NO,BRAND) \
VALUES (1, 'PAGANI')");
conn.commit()
conn.close()
For more information:
https://docs.python.org/2/library/sqlite3.html

Running a entire SQL script via python

I'm looking to run the following test.sql located in a folder on my C: drive. I've been playing with cx_Oracle and just can't get it to work.
test.sql contains the following.
CREATE TABLE MURRAYLR.test
( customer_id number(10) NOT NULL,
customer_name varchar2(50) NOT NULL,
city varchar2(50)
);
CREATE TABLE MURRAYLR.test2
( customer_id number(10) NOT NULL,
customer_name varchar2(50) NOT NULL,
city varchar2(50)
);
This is my code:
import sys
import cx_Oracle
connection = cx_Oracle.connect('user,'password,'test.ora')
cursor = connection.cursor()
f = open("C:\Users\desktop\Test_table.sql")
full_sql = f.read()
sql_commands = full_sql.split(';')
for sql_command in sql_commands:
cursor.execute(sql_command)
cursor.close()
connection.close()

This answer is relevant only if your test.sql file contains new lines '\n\' characters (like mine which I got from copy-pasting your sql code). You will need to remove them in your code, if they are present. To check, do
print full_sql
To fix the '\n's,
sql_commands = full_sql.replace('\n', '').split(';')[:-1]
The above should help.
It removes the '\n's and removes the empty string token at the end when splitting the sql string.

MURRAYLR.test is not acceptable table name in any DBMS I've used. The connection object the cx_oracle.connect returns should already have a schema selected. To switch to a different schema set the current_schema field on the connection object or add using <Schemaname>; in your sql file.
Obviously make sure that the schema exists.

Python with SQLite3: select does not display any data

I am writing a very simply database using python and sqlite3. And when I created a table and some data I wanted to display this data using (in terminal) command "Select * From Data", but no data appears, although I checked using other methods that the data is inserted to the table.
How I create my table and data:
db = connect('database.db')
db_cursor = db.cursor()
db_cursor.execute("CREATE TABLE IF NOT EXISTS Data(Id INT, Name TEXT, City TEXT)")
db_cursor.execute("INSERT INTO Data VALUES (1, 'ABC', 'XYZ')")
If I do:
db_cursor.execute("Select * From Data")
print self.db_cursor.fetchall()
the data is displayed.
But when I run a command line and try to do:
sqlite3 database.db
sqlite> .mode column
sqlite> .headers on
sqlite> SELECT * FROM Data;
no data appears. I checked using
sqlite> .tables
that table is generated correctly.
Why sqlite3 run from command line does not display data?

You need to commit your transaction before it is permanently part of the database:
db.commit()
You can use the database connection as a context manager to commit automatically if a block of code executed successfully:
with db:
db_cursor = db.cursor()
db_cursor.execute("INSERT INTO Data VALUES (1, 'ABC', 'XYZ')")
Note that DDL statements (creating tables and other data definitions) are automatically committed, which is why you saw the table in the database, but not the new row.

How do I insert data into table?

I have created table using this create command as:
CREATE TABLE test_table(id INT PRIMARY KEY,name
VARCHAR(50),price INT)
i want to insert into this table wherein values are stored already in variable
bookdb=# name = 'algorithms'
bookdb-# price = 500
bookdb-# INSERT INTO test_table VALUES(1,'name',price);
I get the following error:
ERROR: syntax error at or near "name"
LINE 1: name = 'algorithms'
Can anyone point out the mistake and propose solution for the above?
Thanks in advance
Edit:
import psycopg2
import file_content
try:
conn = psycopg2.connect(database='bookdb',user='v22')
cur = conn.cursor()
cur.execute("DROP TABLE IF EXISTS book_details")
cur.execute("CREATE TABLE book_details(id INT PRIMARY KEY,name VARCHAR(50),price INT)")
cur.execute("INSERT INTO book_details VALUES(1,'name',price)")
conn.commit()
except:
print "unable to connect to db"
I have used the above code to insert values into table,variables name and price containing the values to be inserted into table are available in file_content python file and i have imported that file.The normal INSERT statement takes values manually but i want my code to take values which are stored in variables.

SQL does not support the concept of variables.
To use variables, you must use a programming language, such as Java, C, Xojo. One such language is PL/pgSQL, which you can think of as a superset of SQL. PL/PgSQL is often bundled as a part of Postgres installers, but not always.
I suggest you read some basic tutorials on SQL.
See this similar question: How do you use script variables in PostgreSQL?

don't have postgres installed here, but you can try this
import psycopg2
import file_content
try:
conn = psycopg2.connect(database='bookdb',user='v22')
cur = conn.cursor()
cur.execute("DROP TABLE IF EXISTS book_details")
cur.execute("CREATE TABLE book_details(id INT PRIMARY KEY,name VARCHAR(50),price INT)")
cur.execute("INSERT INTO book_details VALUES(1, '%s', %s)" % (name, price))
conn.commit()
except:
print "unable to connect to db"

If you are using PSQL console:
\set name 'algo'
\set price 10
insert into test_table values (1,':name',:price)
\g

Create MySQLdb database using Python script

I'm having troubles with creating a database and tables. The database needs to be created within a Python script.
#connect method has 4 parameters:
#localhost (where mysql db is located),
#database user name,
#account password,
#database name
db1 = MS.connect(host="localhost",user="root",passwd="****",db="test")
returns
_mysql_exceptions.OperationalError: (1049, "Unknown database 'test'")
So clearly, the db1 needs to be created first, but how? I've tried CREATE before the connect() statement but get errors.
Once the database is created, how do I create tables?
Thanks,
Tom
Here is the syntax, this works, at least the first time around. The second time naturally returns that the db already exists. Now to figure out how to use the drop command properly.
db = MS.connect(host="localhost",user="root",passwd="****")
db1 = db.cursor()
db1.execute('CREATE DATABASE test1')
So this works great the first time through. The second time through provides a warning "db already exists". How to deal with this? The following is how I think it should work, but doesn't. OR should it be an if statement, looking for if it already exists, do not populate?
import warnings
warnings.filterwarnings("ignore", "test1")

Use CREATE DATABASE to create the database:
db1 = MS.connect(host="localhost",user="root",passwd="****")
cursor = db1.cursor()
sql = 'CREATE DATABASE mydata'
cursor.execute(sql)
Use CREATE TABLE to create the table:
sql = '''CREATE TABLE foo (
bar VARCHAR(50) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
'''
cursor.execute(sql)
There are a lot of options when creating a table. If you are not sure what the right SQL should be, it may help to use a graphical tool like phpmyadmin to create a table, and then use SHOW CREATE TABLE to discover what SQL is needed to create it:
mysql> show create table foo \G
*************************** 1. row ***************************
Table: foo
Create Table: CREATE TABLE `foo` (
`bar` varchar(50) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
phpmyadmin can also show you what SQL it used to perform all sorts of operations. This can be a convenient way to learn some basic SQL.
Once you've experimented with this, then you can write the SQL in Python.

I think the solution is a lot easier, use "if not":
sql = "CREATE DATABASE IF NOT EXISTS test1"
db1.execute(sql)

import MySQLdb
# Open database connection ( If database is not created don't give dbname)
db = MySQLdb.connect("localhost","yourusername","yourpassword","yourdbname" )
# prepare a cursor object using cursor() method
cursor = db.cursor()
# For creating create db
# Below line is hide your warning
cursor.execute("SET sql_notes = 0; ")
# create db here....
cursor.execute("create database IF NOT EXISTS yourdbname")
# create table
cursor.execute("SET sql_notes = 0; ")
cursor.execute("create table IF NOT EXISTS test (email varchar(70),pwd varchar(20));")
cursor.execute("SET sql_notes = 1; ")
#insert data
cursor.execute("insert into test (email,pwd) values('test#gmail.com','test')")
# Commit your changes in the database
db.commit()
# disconnect from server
db.close()
#OUTPUT
mysql> select * from test;
+-----------------+--------+
| email | pwd |
+-----------------+--------+
| test#gmail.com | test |
+-----------------+--------+