allow Paths in save()

altair/utils/save.py

@@ -1,11 +1,13 @@
 import json
+import pathlib
 
 from .mimebundle import spec_to_mimebundle
 
 
 def write_file_or_filename(fp, content, mode="w"):
-    """Write content to fp, whether fp is a string or a file-like object"""
-    if isinstance(fp, str):
+    """Write content to fp, whether fp is a string, a pathlib Path or a
+    file-like object"""
+    if isinstance(fp, str) or isinstance(fp, pathlib.PurePath):
         with open(fp, mode) as f:
             f.write(content)
     else:
@@ -34,8 +36,8 @@ def save(
     ----------
     chart : alt.Chart
         the chart instance to save
-    fp : string filename or file-like object
-        file in which to write the chart.
+    fp : string filename, pathlib.Path or file-like object
+        file to which to write the chart.
     format : string (optional)
         the format to write: one of ['json', 'html', 'png', 'svg'].
         If not specified, the format will be determined from the filename.
@@ -71,6 +73,8 @@ def save(
     if format is None:
         if isinstance(fp, str):
             format = fp.split(".")[-1]
+        elif isinstance(fp, pathlib.PurePath):
+            format = fp.suffix.lstrip(".")
         else:
             raise ValueError(
                 "must specify file format: " "['png', 'svg', 'pdf', 'html', 'json']"

altair/vegalite/v4/tests/test_api.py

@@ -4,6 +4,7 @@
 import json
 import operator
 import os
+import pathlib
 import tempfile
 
 import jsonschema
@@ -284,12 +285,14 @@ def test_save(format, basic_chart):
     fid, filename = tempfile.mkstemp(suffix="." + format)
     os.close(fid)
 
-    try:
-        basic_chart.save(filename)
-        with open(filename, mode) as f:
-            assert f.read()[:1000] == content[:1000]
-    finally:
-        os.remove(filename)
+    # test both string filenames and pathlib.Paths
+    for fp in [filename, pathlib.Path(filename)]:
+        try:
+            basic_chart.save(fp)
+            with open(fp, mode) as f:
+                assert f.read()[:1000] == content[:1000]
+        finally:
+            os.remove(fp)
 
 
 def test_facet_basic():