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I am trying to access the database while the writing to the database from a different script.

The write part

def tick_entry(timestamp,ltp):
    conn = sqlite3.connect('bnf_tick.db', detect_types=sqlite3.PARSE_DECLTYPES, timeout=20)

     c = conn.cursor()

    c.execute('INSERT INTO bnftick (timestamp, close) VALUES (?,?)',
          (timestamp,ltp))

    conn.commit()

    c.close()

    conn.close()

I am running a for loop on a pandas dataframe and writing the data using tick_entry form above.

I want to be able to access the database while the loop is running but I keep getting:

sqlite3.OperationalError: database is locked

In real-time(right now I am feeding in old data) the data should be a little more sporadic. I am trying to figure out if I will be able to access the database while it is being written to by the above function.

Am I doing something wrong?

Thanks

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    Only one connection can have an open write transaction at a time (and when it does no read transactions are allowed unless it's a WAL database) So if one gets a locked error, wait a short time for the transaction to be committed and the write lock released, and try again. Commented Jan 27, 2019 at 17:09
  • @Shawn thanks. Am I correct to assume I can keep the connection to the database in both scripts but while the db is being written into I cannot read it? Commented Jan 27, 2019 at 17:54
  • Unless you use WAL journal mode, yeah. sqlite.org/wal.html Commented Jan 27, 2019 at 20:04

1 Answer 1

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SQLite databases are not able to be modified by more than one process at a time. This is a known design limitation, and is not possible to code around.

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3 Comments

Not true. You can have any number of readers, or a single writer, but not both at once (unless using WAL mode).
@Shawn Thank you for clarifying, I've edited my post to reflect this.
I am only trying to read in the other instance. i.e. one script writes to the SQLite database and the other reads from the DB. Is there a specific way to open in "read only"?

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