Merge pull request #170 from matthiaswenz/conditional-import-sqlite

Load sqlite module only if sqlite connection

Author: rongxin-liu

setup.py

@@ -18,5 +18,5 @@
     package_dir={"": "src"},
     packages=["cs50"],
     url="https://github.com/cs50/python-cs50",
-    version="9.2.2"
+    version="9.2.3"
 )

src/cs50/sql.py

@@ -1,3 +1,4 @@
+import sys
 import threading
 
 # Thread-local data
@@ -51,12 +52,12 @@ def __init__(self, url, **kwargs):
         import re
         import sqlalchemy
         import sqlalchemy.orm
-        import sqlite3
         import threading
 
         # Require that file already exist for SQLite
         matches = re.search(r"^sqlite:///(.+)$", url)
         if matches:
+            import sqlite3
             if not os.path.exists(matches.group(1)):
                 raise RuntimeError("does not exist: {}".format(matches.group(1)))
             if not os.path.isfile(matches.group(1)):
@@ -74,7 +75,7 @@ def __init__(self, url, **kwargs):
         def connect(dbapi_connection, connection_record):
 
             # Enable foreign key constraints
-            if type(dbapi_connection) is sqlite3.Connection:  # If back end is sqlite
+            if "sqlite3" in sys.modules and type(dbapi_connection) is sqlite3.Connection:  # If back end is sqlite
                 cursor = dbapi_connection.cursor()
                 cursor.execute("PRAGMA foreign_keys=ON")
                 cursor.close()