Updates for Regions inputs (#527)

* Allow Regions to be initialize without an argument

* Allow Regions.extend to accept a Regions object

* Check Regions inputs

* Check Regions append and extend inputs

* Add Regions unit tests

* Add changelog entries

CHANGES.rst

@@ -13,12 +13,21 @@ General
 New Features
 ------------
 
+- The ``Regions`` class can now be initialized without any arguments.
+  [#527]
+
+- The ``Regions`` ``extend`` method now can accept another ``Regions``
+  object as input. [#527]
+
 Bug Fixes
 ---------
 
 API Changes
 -----------
 
+- The ``Regions`` class and its ``append`` and ``extend`` methods now
+  raise a ``TypeError`` for invalid inputs. [#527]
+
 
 0.7 (2022-10-27)
 ================

regions/core/regions.py

@@ -24,7 +24,13 @@ class Regions:
         The list of region objects.
     """
 
-    def __init__(self, regions):
+    def __init__(self, regions=(), /):
+        if regions == ():
+            regions = []
+        for item in regions:
+            if not isinstance(item, Region):
+                raise TypeError('Input regions must be a list of Region '
+                                'objects')
         self.regions = regions
 
     def __getitem__(self, index):
@@ -55,6 +61,8 @@ def append(self, region):
         region : `~regions.Region`
             The region to append.
         """
+        if not isinstance(region, Region):
+            raise TypeError('Input region must be a Region object')
         self.regions.append(region)
 
     def extend(self, regions):
@@ -64,10 +72,17 @@ def extend(self, regions):
 
         Parameters
         ----------
-        regions : list of `~regions.Region`
-            A list of regions to include.
+        regions : `~regions.Regions` or list of `~regions.Region`
+            A `~regions.Regions` object or a list of regions to include.
         """
-        self.regions.extend(regions)
+        if isinstance(regions, Regions):
+            self.regions.extend(regions.regions)
+        else:
+            for item in regions:
+                if not isinstance(item, Region):
+                    raise TypeError('Input regions must be a list of Region '
+                                    'objects')
+            self.regions.extend(regions)
 
     def insert(self, index, region):
         """

regions/core/tests/test_regions.py

@@ -0,0 +1,112 @@
+# Licensed under a 3-clause BSD style license - see LICENSE.rst
+"""
+Tests for the regions module.
+"""
+
+import pytest
+from astropy.table import Table
+
+from regions.core import PixCoord, Regions
+from regions.shapes import CirclePixelRegion
+
+
+def test_regions_inputs():
+    regs = []
+    for radius in range(1, 5):
+        center = PixCoord(14, 21)
+        regs.append(CirclePixelRegion(center, radius=radius))
+
+    regions = Regions(regs)
+    assert len(regions) == 4
+
+
+def test_regions_no_input():
+    regions = Regions()
+    assert len(regions) == 0
+
+    regions = Regions([])
+    assert len(regions) == 0
+
+
+def test_regions_invalid_input():
+    match = "'int' object is not iterable"
+    with pytest.raises(TypeError, match=match):
+        Regions(1)
+
+    match = 'Input regions must be a list of Region objects'
+    with pytest.raises(TypeError, match=match):
+        Regions([1])
+    with pytest.raises(TypeError, match=match):
+        Regions([1, 2, 3])
+
+
+def test_regions_append():
+    regions = Regions()
+
+    for radius in range(1, 5):
+        center = PixCoord(14, 21)
+        regions.append(CirclePixelRegion(center, radius=radius))
+    assert len(regions) == 4
+
+    match = 'Input region must be a Region object'
+    with pytest.raises(TypeError, match=match):
+        regions.append(1)
+
+
+def test_regions_extend():
+    regions = Regions()
+
+    regs = []
+    for radius in range(1, 5):
+        center = PixCoord(14, 21)
+        regs.append(CirclePixelRegion(center, radius=radius))
+
+    regions.extend(regs)
+    assert len(regions) == 4
+
+    regions.extend(regions)
+    assert len(regions) == 8
+
+    match = 'Input regions must be a list of Region objects'
+    with pytest.raises(TypeError, match=match):
+        regions.extend([1])
+
+
+def test_regions_methods():
+    regions = Regions()
+
+    for radius in range(1, 5):
+        center = PixCoord(14, 21)
+        regions.append(CirclePixelRegion(center, radius=radius))
+
+    reg_slc = regions[0:2]
+    assert len(reg_slc) == 2
+
+    reg = CirclePixelRegion(PixCoord(0, 0), radius=1)
+    regions.insert(0, reg)
+    assert len(regions) == 5
+    assert regions[0] == reg
+
+    regions2 = regions.copy()
+    regions.reverse()
+    assert regions.regions == regions2.regions[::-1]
+
+    outreg = regions.pop(-1)
+    assert outreg == reg
+
+
+def test_regions_get_formats():
+    reg = CirclePixelRegion(PixCoord(0, 0), radius=1)
+    regions = Regions([reg])
+    tbl = regions.get_formats()
+    assert isinstance(tbl, Table)
+    assert len(tbl) == 3
+
+
+def test_regions_repr():
+    reg = CirclePixelRegion(PixCoord(0, 0), radius=1)
+    regions = Regions([reg])
+    regions_str = '[<CirclePixelRegion(center=PixCoord(x=0, y=0), radius=1)>]'
+    regions_repr = f'<Regions({regions_str})>'
+    assert str(regions) == regions_str
+    assert repr(regions) == regions_repr