file is not a database

What this means

SQLITE_NOTADB (result code 26) is returned when SQLite opens a file that does not begin with the expected SQLite database header magic bytes ("SQLite format 3\000"). This happens when the application accidentally opens a non-database file (a CSV, a JSON file, a PDF) using sqlite3.connect(), or when an encrypted database is opened without the decryption key.

Why it happens

1. 1The file path points to a non-SQLite file (text file, binary, etc.)
2. 2The database file is encrypted (e.g., SQLCipher) and is being opened without the key
3. 3The file is a SQLite database but uses a page size or header format from an incompatible fork
4. 4The file was partially written and the header is incomplete

How to reproduce

sqlite3.connect() is called on a plain text file.

import sqlite3

# Create a text file, not a database
with open('/tmp/notadb.txt', 'w') as f:
    f.write('this is not a database\n')

conn = sqlite3.connect('/tmp/notadb.txt')
conn.execute('SELECT * FROM t')  # triggers SQLITE_NOTADB

Fix 1: Verify the file is a valid SQLite database before connecting

When the file path may be wrong or the file type is uncertain.

import sqlite3

def is_sqlite_db(path):
    try:
        with open(path, 'rb') as f:
            header = f.read(16)
        return header == b'SQLite format 3\x00'
    except OSError:
        return False

if is_sqlite_db('/tmp/mydb.db'):
    conn = sqlite3.connect('/tmp/mydb.db')
else:
    raise ValueError("Not a valid SQLite database file")

What not to do

Version notes

Sources

Confidence assessment

See also