Is there a way to get a schema of a database from within python?

Question

I\'m trying to find out a way to find the names of tables in a database(if any exist). I find that from a sqlite cli I can use:

>.tables

<

Answer 1

Here's a convenient printer I wrote based Martijn's response:

def printSchema(connection):
    for (tableName,) in connection.execute(
        """
        select NAME from SQLITE_MASTER where TYPE='table' order by NAME;
        """
    ):
        print("{}:".format(tableName))
        for (
            columnID, columnName, columnType,
            columnNotNull, columnDefault, columnPK,
        ) in connection.execute("pragma table_info('{}');".format(tableName)):
            print("  {id}: {name}({type}){null}{default}{pk}".format(
                id=columnID,
                name=columnName,
                type=columnType,
                null=" not null" if columnNotNull else "",
                default=" [{}]".format(columnDefault) if columnDefault else "",
                pk=" *{}".format(columnPK) if columnPK else "",
            ))

Answer 2

result sets have a description that you can get some information from. It reveals some basic metadata like column name and number of columns.

>>> rs = c.execute('''SELECT * FROM news WHERE 1=0''');
>>> dir(rs)
['__class__', '__delattr__', '__doc__', '__format__',  
'__getattribute__', '__hash__', '__init__', '__iter__', '__new__',  
'__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__',
'__str__', '__subclasshook__', 'arraysize', 'close', 'connection',
**'description'**, 'execute', 'executemany', 'executescript', 'fetchall',
'fetchmany', 'fetchone', 'lastrowid', 'next', 'row_factory',
'rowcount', 'setinputsizes', 'setoutputsize']



>>> print(rs.description)
(('id', None, None, None, None, None, None), 
('imageUrl', None, None, None, None, None, None), 
('headline', None, None, None, None, None, None), 
('who', None, None, None, None, None, None))

Answer 3

Use sqlite row object. A row object has keys() that will give you the schema.

from docs.python.org

conn.row_factory = sqlite3.Row
c = conn.cursor()
c.execute('select * from stocks')
  <sqlite3.Cursor object at 0x7f4e7dd8fa80>
r = c.fetchone()
type(r)
  <type 'sqlite3.Row'>
  r
  (u'2006-01-05', u'BUY', u'RHAT', 100.0, 35.14)
r.keys()
  ['date', 'trans', 'symbol', 'qty', 'price']

Answer 4

You should be able access the table names from the sqlite_master table.

SELECT name FROM sqlite_master WHERE type='table';

The names of the columns are not directly accessible. The easiest way to get them is to query the table and get the column names from the query result.

SELECT * FROM table_name LIMIT 1;

Answer 5

I just tried

SELECT name FROM my_db.sqlite_master WHERE type='table';

to combine Tom Kerr's answer and the attempt to retrieve information on an attached database. At first it didn't work. Turns out I first have to attach the other database this way:

ATTACH DATABASE 'file:my_other_database_file.db?cache=shared' as my_db;

otherwise the database will fail to obtain a read lock for the attached database's sqlite_master (and all queries will succeed with zero results). Just a hint in case anybody else stumbles upon that part of the issue.

Answer 6

To get the schema information, IMHO, below also works:

select sql from sqlite_master where type='table';