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Use libsqlite3 directly from Python with ctypes: without using the built-in sqlite3 Python package, and without compiling anything
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# From https://stackoverflow.com/a/68876046/1319998, which is itself inspired by https://stackoverflow.com/a/68814418/1319998 | |
from contextlib import contextmanager | |
from collections import namedtuple | |
from ctypes import cdll, byref, string_at, c_char_p, c_int, c_double, c_int64, c_void_p | |
from ctypes.util import find_library | |
from sys import platform | |
def query(db_file, sql, params=()): | |
libsqlite3 = cdll.LoadLibrary(find_library('sqlite3')) | |
libsqlite3.sqlite3_errstr.restype = c_char_p | |
libsqlite3.sqlite3_errmsg.restype = c_char_p | |
libsqlite3.sqlite3_column_name.restype = c_char_p | |
libsqlite3.sqlite3_column_double.restype = c_double | |
libsqlite3.sqlite3_column_int64.restype = c_int64 | |
libsqlite3.sqlite3_column_blob.restype = c_void_p | |
libsqlite3.sqlite3_column_bytes.restype = c_int64 | |
SQLITE_ROW = 100 | |
SQLITE_DONE = 101 | |
SQLITE_TRANSIENT = -1 | |
SQLITE_OPEN_READWRITE = 0x00000002 | |
bind = { | |
type(0): libsqlite3.sqlite3_bind_int64, | |
type(0.0): libsqlite3.sqlite3_bind_double, | |
type(''): lambda pp_stmt, i, value: libsqlite3.sqlite3_bind_text(pp_stmt, i, value.encode('utf-8'), len(value.encode('utf-8')), SQLITE_TRANSIENT), | |
type(b''): lambda pp_stmt, i, value: libsqlite3.sqlite3_bind_blob(pp_stmt, i, value, len(value), SQLITE_TRANSIENT), | |
type(None): lambda pp_stmt, i, _: libsqlite3.sqlite3_bind_null(pp_stmt, i), | |
} | |
extract = { | |
1: libsqlite3.sqlite3_column_int64, | |
2: libsqlite3.sqlite3_column_double, | |
3: lambda pp_stmt, i: string_at( | |
libsqlite3.sqlite3_column_blob(pp_stmt, i), | |
libsqlite3.sqlite3_column_bytes(pp_stmt, i), | |
).decode(), | |
4: lambda pp_stmt, i: string_at( | |
libsqlite3.sqlite3_column_blob(pp_stmt, i), | |
libsqlite3.sqlite3_column_bytes(pp_stmt, i), | |
), | |
5: lambda pp_stmt, i: None, | |
} | |
def run(func, *args): | |
res = func(*args) | |
if res != 0: | |
raise Exception(libsqlite3.sqlite3_errstr(res).decode()) | |
def run_with_db(db, func, *args): | |
if func(*args) != 0: | |
raise Exception(libsqlite3.sqlite3_errmsg(db).decode()) | |
@contextmanager | |
def get_db(db_file): | |
db = c_void_p() | |
run(libsqlite3.sqlite3_open_v2, db_file.encode(), byref(db), SQLITE_OPEN_READWRITE, None) | |
try: | |
yield db | |
finally: | |
run_with_db(db, libsqlite3.sqlite3_close, db) | |
@contextmanager | |
def get_pp_stmt(db, sql): | |
pp_stmt = c_void_p() | |
run_with_db(db, libsqlite3.sqlite3_prepare_v3, db, sql.encode(), -1, 0, byref(pp_stmt), None) | |
try: | |
yield pp_stmt | |
finally: | |
run_with_db(db, libsqlite3.sqlite3_finalize, pp_stmt) | |
with \ | |
get_db(db_file) as db, \ | |
get_pp_stmt(db, sql) as pp_stmt: | |
for i, param in enumerate(params): | |
run_with_db(db, bind[type(param)], pp_stmt, i + 1, param) | |
row_constructor = namedtuple('Row', ( | |
libsqlite3.sqlite3_column_name(pp_stmt, i).decode() | |
for i in range(0, libsqlite3.sqlite3_column_count(pp_stmt)) | |
)) | |
while True: | |
res = libsqlite3.sqlite3_step(pp_stmt) | |
if res == SQLITE_DONE: | |
break | |
if res != SQLITE_ROW: | |
raise Exception(libsqlite3.sqlite3_errstr(res).decode()) | |
yield row_constructor(*( | |
extract[libsqlite3.sqlite3_column_type(pp_stmt, i)](pp_stmt, i) | |
for i in range(0, len(row_constructor._fields)) | |
)) |
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P.S. I have gained a lot from your example /jsok/ above. That has offered a lot of hints :)
Thank you.