在python3 sqlite中加载sqlite3扩展

Question

How does one correctly load a sqlite extension into python sqlite import?

os: Windows 7 64bit
sqlite3 version: 3.14.1 64bit
python3 version: 3.5.2 64bit

Here is my process so far: compile extension-functions.c to libsqlitefunctions.dll using this command:

gcc -shared -I "C:\Software\sqlite3\sqlite-master" -o libsqlitefunctions.dll extension-functions.c

Then I can happily use these functions in sqlite3 command line using this command:

SELECT load_extension('libsqlitefunctions.dll');

However when trying in the python script:

import sqlite3 as lite
con = lite.connect(db_file)
con.enable_load_extension(True)
con.load_extension("<<path to file>>\\libsqlitefunctions.dll")

This error appears:

Error The specified module could not be found. :

The extension-functions.c file does include the COMPILE_SQLITE_EXTENSIONS_AS_LOADABLE_MODULE section, and in fact it loads fine when using command line sqlite3

Additional notes:
The python sqlite package is installed and working correctly.
I've also tried updating the sqlite3.dll in the python path to the latest version

Answer 1

This isn't a nice answer, but it provides a method to use the extension in python.

Output sql commands to a file, then use subprocess to run the file directly into the command line, like so:

import subprocess
import uuid
import os

db_file = "trial02.db"
sqlite_functions_file = "libsqlitefunctions.dll"

sql_file = uuid.uuid4() + ".sql"
with open(sql_file, 'w') as fsql:
    fsql.write('/* auto script */\n\n')
    #load extension
    sql = "SELECT load_extension('" + sqlite_functions_file + "');"
    fsql.write(sql + '\n')
    #sql scripts
    sql = "insert into t(c) values (log(2));"
    fsql.write(sql + '\n')

args = [
    'sqlite3'
    , db_file
    , '< ', sql_file
]
print(' '.join(args))
out1 = subprocess.run(' '.join(args), shell=True)
os.remove(sql_file)

Answer 2

Place libsqlitefunctions.dll in a folder that is visible globally like c:\\WINDOWS\\ or some other folder from the PATH environment variable. Then you will be able to load the extension using simple command:

con.load_extension("libsqlitefunctions.dll")