ENH: Check that the lengths of the inputs to histogram2d are the same. (#20228)

Improves exception message when inputs have different shapes.

Closes gh-20050

Co-authored-by: Ross Barnowski <rossbar@berkeley.edu>

2 files changed, 13 insertions, 0 deletions

diff --git a/numpy/lib/tests/test_twodim_base.py b/numpy/lib/tests/test_twodim_base.py
index cce683bfe..c1c5a1615 100644
--- a/numpy/lib/tests/test_twodim_base.py
+++ b/numpy/lib/tests/test_twodim_base.py
@@ -18,6 +18,9 @@ import numpy as np
 from numpy.core.tests.test_overrides import requires_array_function
 
 
+import pytest
+
+
 def get_mat(n):
     data = arange(n)
     data = add.outer(data, data)
@@ -295,6 +298,13 @@ class TestHistogram2d:
         r = histogram2d(xy, xy, weights=s_d)
         assert_(r, ((ShouldDispatch,), (xy, xy), dict(weights=s_d)))
 
+    @pytest.mark.parametrize(("x_len", "y_len"), [(10, 11), (20, 19)])
+    def test_bad_length(self, x_len, y_len):
+        x, y = np.ones(x_len), np.ones(y_len)
+        with pytest.raises(ValueError,
+                           match='x and y must have the same length.'):
+            histogram2d(x, y)
+
 
 class TestTri:
     def test_dtype(self):
diff --git a/numpy/lib/twodim_base.py b/numpy/lib/twodim_base.py
index 811faff79..3e5ad31ff 100644
--- a/numpy/lib/twodim_base.py
+++ b/numpy/lib/twodim_base.py
@@ -804,6 +804,9 @@ def histogram2d(x, y, bins=10, range=None, normed=None, weights=None,
     >>> plt.show()
     """
     from numpy import histogramdd
+    
+    if len(x) != len(y):
+        raise ValueError('x and y must have the same length.')
 
     try:
         N = len(bins)