Loading large mysql select statements into python

I have two mysql databases called database A and database B. I want to use python to copy all the data from a table in database A to a table in database B. The datatable holds approximately 5M rows. I have written the following code:

connection = make_connection(source_db)
c = connection.cursor()
batch_size = 100000
while True:
    batch = c.fetchmany(batch_size)
    print('Extracted a batch.')
    if not batch:
        break
    insert_data(batch)

connection.close()

I ran this code and it takes minutes for fetchmany() to extract a single batch. I've tried to use fetchall() without the while True statement but this takes even longer.

Question: How do I successfully speed up this process/what is the best way to load large select statements into python?

Copyright License：
Author:「Mr. President」,Reproduced under the CC 4.0 BY-SA copyright license with link to original source & disclaimer.
Link to：https://stackoverflow.com/questions/53206405/loading-large-mysql-select-statements-into-python