Python sqlite3：如何检查连接是否是内存数据库？

Question

From Python's sqlite3 library, how can we determine if a connection belongs to a in-memory database?

import sqlite3

conn = sqlite3.connect(':memory:')

def is_in_memory_connection(conn):
    # How to check if `conn` is an in-memory connection?

Is it possible to check the filename of an on-disk database? If so, I would presume that it would return None for an in-memory database.

Answer 1

This is the closest I could come up with:

import sqlite3
 
def is_in_memory_connection(conn):
    local_cursor = conn.cursor()
    local_cursor.execute('pragma database_list')
    rows = local_cursor.fetchall()                                                       
    print(rows[0][2])
    return rows[0][2] == ''
 
#database = 'test.sqlite'
database = ':memory:'
conn = sqlite3.connect(database)
result = is_in_memory_connection(conn)
 
print(result)

If you have an in-memory database, database_list will show equivalent of this:

sqlite> pragma database_list;
seq  name  file
---  ----  ----
0    main      

If you are opening a file that's on disk, it'll show the path of the file equivalent of this:

sqlite> pragma database_list;
seq  name  file                      
---  ----  --------------------------
0    main  /home/testing/test.sqlite

Taking advantage of this, you could call pragma database_list to show the file. If the path is empty, the database is not associated with a file.

https://sqlite.org/pragma.html#pragma_database_list