DEP: make fiona import truly lazy (on first usage) (#2427)

geopandas/io/file.py

@@ -11,30 +11,8 @@ import pyproj
 from shapely.geometry import mapping
 from shapely.geometry.base import BaseGeometry
 
-try:
-    import fiona
-
-    fiona_import_error = None
-
-    # only try to import fiona.Env if the main fiona import succeeded (otherwise you
-    # can get confusing "AttributeError: module 'fiona' has no attribute '_loading'"
-    # / partially initialized module errors)
-    try:
-        from fiona import Env as fiona_env
-    except ImportError:
-        try:
-            from fiona import drivers as fiona_env
-        except ImportError:
-            fiona_env = None
-
-except ImportError as err:
-    fiona = None
-    fiona_import_error = str(err)
-
-
 from geopandas import GeoDataFrame, GeoSeries
 
-
 # Adapted from pandas.io.common
 from urllib.request import urlopen as _urlopen
 from urllib.parse import urlparse as parse_url
@@ -44,6 +22,37 @@ from urllib.parse import uses_netloc, uses_params, uses_relative
 _VALID_URLS = set(uses_relative + uses_netloc + uses_params)
 _VALID_URLS.discard("")
 
+
+fiona = None
+fiona_env = None
+fiona_import_error = None
+
+
+def _import_fiona():
+    global fiona
+    global fiona_env
+    global fiona_import_error
+
+    if fiona is None:
+        try:
+            import fiona
+
+            # only try to import fiona.Env if the main fiona import succeeded
+            # (otherwise you can get confusing "AttributeError: module 'fiona'
+            # has no attribute '_loading'" / partially initialized module errors)
+            try:
+                from fiona import Env as fiona_env
+            except ImportError:
+                try:
+                    from fiona import drivers as fiona_env
+                except ImportError:
+                    fiona_env = None
+
+        except ImportError as err:
+            fiona = False
+            fiona_import_error = str(err)
+
+
 _EXTENSION_TO_DRIVER = {
     ".bna": "BNA",
     ".dxf": "DXF",
@@ -164,6 +173,7 @@ def _read_file(filename, bbox=None, mask=None, rows=None, **kwargs):
     may fail. In this case, the proper encoding can be specified explicitly
     by using the encoding keyword parameter, e.g. ``encoding='utf-8'``.
     """
+    _import_fiona()
     _check_fiona("'read_file' function")
     filename = _expand_user(filename)
 
@@ -357,6 +367,7 @@ def _to_file(
     may fail. In this case, the proper encoding can be specified explicitly
     by using the encoding keyword parameter, e.g. ``encoding='utf-8'``.
     """
+    _import_fiona()
     _check_fiona("'to_file' method")
     filename = _expand_user(filename)
 

geopandas/io/tests/test_file.py

@@ -16,7 +16,7 @@ from shapely.geometry import Point, Polygon, box
 
 import geopandas
 from geopandas import GeoDataFrame, read_file
-from geopandas.io.file import fiona_env, _detect_driver, _EXTENSION_TO_DRIVER
+from geopandas.io.file import _detect_driver, _EXTENSION_TO_DRIVER
 
 from geopandas.testing import assert_geodataframe_equal, assert_geoseries_equal
 from geopandas.tests.util import PACKAGE_DIR, validate_boro_df
@@ -654,6 +654,7 @@ def test_read_file_filtered_with_gdf_boundary_mismatched_crs__mask(df_nybb):
 
 
 def test_read_file_empty_shapefile(tmpdir):
+    from geopandas.io.file import fiona_env
 
     # create empty shapefile
     meta = {