Backport PR #27511 on branch 0.25.x (BUG: display.precision of negative complex numbers)

doc/source/whatsnew/v0.25.1.rst

@@ -57,6 +57,7 @@ Timezones
 Numeric
 ^^^^^^^
 - Bug in :meth:`Series.interpolate` when using a timezone aware :class:`DatetimeIndex` (:issue:`27548`)
+- Bug when printing negative floating point complex numbers would raise an ``IndexError`` (:issue:`27484`)
 -
 -
 

pandas/core/frame.py

@@ -2601,12 +2601,12 @@ def memory_usage(self, index=True, deep=False):
         ...              for t in dtypes])
         >>> df = pd.DataFrame(data)
         >>> df.head()
-           int64  float64  complex128  object  bool
-        0      1      1.0    1.0+0.0j       1  True
-        1      1      1.0    1.0+0.0j       1  True
-        2      1      1.0    1.0+0.0j       1  True
-        3      1      1.0    1.0+0.0j       1  True
-        4      1      1.0    1.0+0.0j       1  True
+           int64  float64            complex128  object  bool
+        0      1      1.0    1.000000+0.000000j       1  True
+        1      1      1.0    1.000000+0.000000j       1  True
+        2      1      1.0    1.000000+0.000000j       1  True
+        3      1      1.0    1.000000+0.000000j       1  True
+        4      1      1.0    1.000000+0.000000j       1  True
 
         >>> df.memory_usage()
         Index           128

pandas/io/formats/format.py

@@ -5,6 +5,7 @@
 
 from functools import partial
 from io import StringIO
+import re
 from shutil import get_terminal_size
 from unicodedata import east_asian_width
 
@@ -1584,17 +1585,10 @@ def _trim_zeros_complex(str_complexes, na_rep="NaN"):
     Separates the real and imaginary parts from the complex number, and
     executes the _trim_zeros_float method on each of those.
     """
-
-    def separate_and_trim(str_complex, na_rep):
-        num_arr = str_complex.split("+")
-        return (
-            _trim_zeros_float([num_arr[0]], na_rep)
-            + ["+"]
-            + _trim_zeros_float([num_arr[1][:-1]], na_rep)
-            + ["j"]
-        )
-
-    return ["".join(separate_and_trim(x, na_rep)) for x in str_complexes]
+    return [
+        "".join(_trim_zeros_float(re.split(r"([j+-])", x), na_rep))
+        for x in str_complexes
+    ]
 
 
 def _trim_zeros_float(str_floats, na_rep="NaN"):

pandas/tests/io/formats/test_format.py

@@ -1537,22 +1537,24 @@ def test_to_string_float_index(self):
         assert result == expected
 
     def test_to_string_complex_float_formatting(self):
-        # GH #25514
+        # GH #25514, 25745
         with pd.option_context("display.precision", 5):
             df = DataFrame(
                 {
                     "x": [
                         (0.4467846931321966 + 0.0715185102060818j),
                         (0.2739442392974528 + 0.23515228785438969j),
                         (0.26974928742135185 + 0.3250604054898979j),
+                        (-1j),
                     ]
                 }
             )
             result = df.to_string()
             expected = (
                 "                  x\n0  0.44678+0.07152j\n"
                 "1  0.27394+0.23515j\n"
-                "2  0.26975+0.32506j"
+                "2  0.26975+0.32506j\n"
+                "3 -0.00000-1.00000j"
             )
             assert result == expected