BUG: Fixes #54617 Dataframe to html for empty array with complex dtypes

pandas/io/formats/format.py

@@ -1960,6 +1960,8 @@ def _trim_zeros_complex(str_complexes: np.ndarray, decimal: str = ".") -> list[s
     # in the array
     n = len(str_complexes)
     padded_parts = _trim_zeros_float(real_part + imag_part, decimal)
+    if len(padded_parts) == 0:
+        return []
     padded_length = max(len(part) for part in padded_parts) - 1
     padded = [
         real_pt  # real part, possibly NaN

pandas/tests/io/formats/test_to_html.py

@@ -959,3 +959,14 @@ def test_to_html_tuple_col_with_colspace():
         "</table>"
     )
     assert result == expected
+
+
+def test_to_html_empty_complex_array():
+    # GH#54167
+    df = DataFrame({"x": np.array([], dtype="complex")})
+    html_op = df.to_html(col_space=100)
+    result = hashlib.md5(b"html_op").hexdigest()
+    expected = "9d81f92dbc2d9f2f4876900c09559c39"
+    #'<table border="1" class="dataframe">\n  <thead>\n    <tr style="text-align: right;">\n      <th></th>\n      <th>x</th>\n    </tr>\n  </thead>\n  <tbody>\n  </tbody>\n</table>'
+    print("--assserting")
+    assert result == expected