Storing information in a file, Python - 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

Related

Continue executing sql statements if error found python sqlite3

I have a file containing sql commands and I want to execute the commands given in the file and if any command throws any error then ignore the error and execute the next command.
Here is a sample file:
drop table department;
drop table classroom;
create table classroom
(building varchar(15),
room_number varchar(7),
capacity numeric(4,0),
primary key (building, room_number)
);
create table department
(dept_name varchar(20),
building varchar(15),
budget numeric(12,2) check (budget > 0),
primary key (dept_name)
);
For eg. if the classroom table doesn't exists then the drop table command will produce an error and the program will terminate. I want that the program keep running and execute all commands in the file.
The problem I'm facing is that the create table command is in multiple lines so I don't know how to execute that.
Take a look at the sqlite3 manual:
import sqlite3
con = sqlite3.connect(":memory:")
cur = con.cursor()
with open('PATH_TO_SQL_FILE', 'r') as fp:
text = fp.read().split(';')
for command in text:
try:
cur.execute(command)
except sqlite3.Error:
pass
import sqlite3
#define connection and cursor
connection = sqlite3.connect ('test_db')
cursor =connection.cursor()
command1 ="""create table classroom
(building varchar(15),
room_number varchar(7),
capacity numeric(4,0),
primary key (building, room_number)
)"""
cursor.execute(command1)
command2 ="""create table department
(dept_name varchar(20),
building varchar(15),
budget numeric(12,2) check (budget > 0),
primary key (dept_name)
)"""
cursor.execute(command2)

SQLite-Manager on Firefox and Python

I have written a small test application using SQLite with Python 3.3:
import sqlite3
MDB = sqlite3.connect('D:\MDB.db') # create the db object
cursor = MDB.cursor() # assign a cursor
cursor.execute('''CREATE TABLE IF NOT EXISTS section (
Code INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
Description TEXT )
''')
cursor.execute('''DELETE FROM section''') # delete contents for reruns
cursor.execute('''INSERT INTO section
(Description)
VALUES (?)
''', ('Abdul, Paula',))
cursor.execute('''INSERT INTO section
(Description)
VALUES (?)
''', ('ABWH',))
print('Results:\n')
cursor.execute('''SELECT * FROM section''')
selection = cursor.fetchall()
for row in selection:
print('\t', row)
The SELECT statement shows the results expected (seeming to indicate that the row exists), but if I connect to the database with SQLite-Manager, the table exists but is empty, and if I try the same query with another script connected to the database, nothing is returned. Can anyone please explain what I am doing wrong?
You're not saving changes (calling MDB.commit).

Python and PostgreSQL - GeomFromText

I'm a Python learner,
I'm trying to insert geometry records into PostgreSQL.
If I tried the query without the geometry column, it works fine and all data inserted successfully.
cur.execute("INSERT INTO taxi (userid,carNum) SELECT '"+str(msg['UserID'])+"',"+str(msg['CarNumber']))
Once I try to add the geometry records, nothing happens! execution ends without errors but nothing being inserted into DB.
cur.execute("INSERT INTO taxi (position,userid,carNum) SELECT GeomFromText('POINT("+str(float(msg['longitude']))+" "+str(float(msg['latitude']))+")',4326),'"+str(msg['UserID'])+"',"+str(msg['CarNumber']))
Couldn't figure out what I'm missing here
You need to commit the data to the database.
Check the documentation of psycopg2 http://initd.org/psycopg/docs/usage.html#passing-parameters-to-sql-queries
Follow those steps
>>> import psycopg2
# Connect to an existing database
>>> conn = psycopg2.connect("dbname=test user=postgres")
# Open a cursor to perform database operations
>>> cur = conn.cursor()
# Execute a command: this creates a new table
>>> cur.execute("CREATE TABLE test (id serial PRIMARY KEY, num integer, data varchar);")
# Pass data to fill a query placeholders and let Psycopg perform
# the correct conversion (no more SQL injections!)
>>> cur.execute("INSERT INTO test (num, data) VALUES (%s, %s)",
... (100, "abc'def"))
# Query the database and obtain data as Python objects
>>> cur.execute("SELECT * FROM test;")
>>> cur.fetchone()
(1, 100, "abc'def")
# Make the changes to the database persistent
>>> conn.commit()
# Close communication with the database
>>> cur.close()
>>> conn.close()

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

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