Allow png factory to save to a string path

Fixes #306

CHANGES.rst

@@ -5,7 +5,8 @@ Change log
 7.5 (unreleased)
 ================
 
-- Nothing changed yet.
+- Allow ``pypng`` factory to allow for saving to a string (like
+  ``qr.save("some_file.png")``) in addition to file-like objects. 
 
 
 7.4.1 (3 February 2023)

qrcode/image/pure.py

@@ -23,6 +23,8 @@ def drawrect(self, row, col):
         """
 
     def save(self, stream, kind=None):
+        if isinstance(stream, str):
+            stream = open(stream, "wb")
         self._img.write(stream, self.rows_iter())
 
     def rows_iter(self):

qrcode/tests/test_qrcode.py

@@ -184,6 +184,18 @@ def test_render_pypng(self):
         print(img.width, img.box_size, img.border)
         img.save(io.BytesIO())
 
+    def test_render_pypng_to_str(self):
+        qr = qrcode.QRCode()
+        qr.add_data(UNICODE_TEXT)
+        img = qr.make_image(image_factory=PyPNGImage)
+        self.assertIsInstance(img.get_image(), png.Writer)
+
+        mock_open = mock.mock_open()
+        with mock.patch("qrcode.image.pure.open", mock_open, create=True):
+            img.save("test_file.png")
+        mock_open.assert_called_once_with("test_file.png", "wb")
+        mock_open("test_file.png", "wb").write.assert_called()
+
     @unittest.skipIf(not pil_Image, "Requires PIL")
     def test_render_styled_Image(self):
         qr = qrcode.QRCode(error_correction=qrcode.ERROR_CORRECT_L)