find_spatialite() utility function, closes #135

docs/python-api.rst

@@ -1298,3 +1298,23 @@ For example:
     #    [age] INTEGER,
     #    [thumbnail] BLOB
     # )
+
+.. _find_spatialite:
+
+Finding SpatiaLite
+==================
+
+The ``find_spatialite()`` function searches for the `SpatiaLite <https://www.gaia-gis.it/fossil/libspatialite/index>`__ SQLite extension in some common places. It returns a string path to the location, or ``None`` if SpatiaLite was not found.
+
+You can use it in code like this:
+
+.. code-block:: python
+
+    from sqlite_utils import Database
+    from sqlite_utils.utils import find_spatialite
+
+    db = Database("mydb.db")
+    spatialite = find_spatialite()
+    if spatialite:
+        db.conn.enable_load_extension(True)
+        db.conn.load_extension(spatialite)

sqlite_utils/utils.py

@@ -1,4 +1,5 @@
 import base64
+import os
 
 try:
     import pysqlite3 as sqlite3
@@ -10,6 +11,11 @@ except ImportError:
 
     OperationalError = sqlite3.OperationalError
 
+SPATIALITE_PATHS = (
+    "/usr/lib/x86_64-linux-gnu/mod_spatialite.so",
+    "/usr/local/lib/mod_spatialite.dylib",
+)
+
 
 def suggest_column_types(records):
     all_column_types = {}
@@ -74,3 +80,10 @@ def decode_base64_values(doc):
     if not to_fix:
         return doc
     return dict(doc, **{k: base64.b64decode(doc[k]["encoded"]) for k in to_fix})
+
+
+def find_spatialite():
+    for path in SPATIALITE_PATHS:
+        if os.path.exists(path):
+            return path
+    return None

tests/test_utils.py

@@ -20,3 +20,8 @@ def test_decode_base64_values(input, expected, should_be_is):
         assert actual is input
     else:
         assert actual == expected
+
+
+def test_find_spatialite():
+    spatialite = utils.find_spatialite()
+    assert spatialite is None or isinstance(spatialite, str)