BUG: repr of inf values with use_inf_as_na

doc/source/whatsnew/v2.2.0.rst

@@ -394,6 +394,7 @@ Other
 ^^^^^
 - Bug in :func:`cut` incorrectly allowing cutting of timezone-aware datetimes with timezone-naive bins (:issue:`54964`)
 - Bug in :meth:`DataFrame.apply` where passing ``raw=True`` ignored ``args`` passed to the applied function (:issue:`55009`)
+- Bug in rendering ``inf`` values inside a a :class:`DataFrame` with the ``use_inf_as_na`` option enabled (:issue:`55483`)
 - Bug in rendering a :class:`Series` with a :class:`MultiIndex` when one of the index level's names is 0 not having that name displayed (:issue:`55415`)
 -
 

pandas/_libs/missing.pyi

@@ -14,4 +14,3 @@ def isneginf_scalar(val: object) -> bool: ...
 def checknull(val: object, inf_as_na: bool = ...) -> bool: ...
 def isnaobj(arr: np.ndarray, inf_as_na: bool = ...) -> npt.NDArray[np.bool_]: ...
 def is_numeric_na(values: np.ndarray) -> npt.NDArray[np.bool_]: ...
-def is_float_nan(values: np.ndarray) -> npt.NDArray[np.bool_]: ...

pandas/_libs/missing.pyx

@@ -255,31 +255,6 @@ cdef bint checknull_with_nat_and_na(object obj):
     return checknull_with_nat(obj) or obj is C_NA
 
 
-@cython.wraparound(False)
-@cython.boundscheck(False)
-def is_float_nan(values: ndarray) -> ndarray:
-    """
-    True for elements which correspond to a float nan
-
-    Returns
-    -------
-    ndarray[bool]
-    """
-    cdef:
-        ndarray[uint8_t] result
-        Py_ssize_t i, N
-        object val
-
-    N = len(values)
-    result = np.zeros(N, dtype=np.uint8)
-
-    for i in range(N):
-        val = values[i]
-        if util.is_nan(val):
-            result[i] = True
-    return result.view(bool)
-
-
 @cython.wraparound(False)
 @cython.boundscheck(False)
 def is_numeric_na(values: ndarray) -> ndarray:

pandas/core/indexes/base.py

@@ -37,7 +37,6 @@
     is_datetime_array,
     no_default,
 )
-from pandas._libs.missing import is_float_nan
 from pandas._libs.tslibs import (
     IncompatibleFrequency,
     OutOfBoundsDatetime,
@@ -1390,16 +1389,8 @@ def _format_with_header(self, *, header: list[str_t], na_rep: str_t) -> list[str
 
         if is_object_dtype(values.dtype) or is_string_dtype(values.dtype):
             values = np.asarray(values)
-            values = lib.maybe_convert_objects(values, safe=True)
-
-            result = [pprint_thing(x, escape_chars=("\t", "\r", "\n")) for x in values]
-
-            # could have nans
-            mask = is_float_nan(values)
-            if mask.any():
-                result_arr = np.array(result)
-                result_arr[mask] = na_rep
-                result = result_arr.tolist()
+            # TODO: why do we need different justify for these cases?
+            result = trim_front(format_array(values, None, justify="all"))
         else:
             result = trim_front(format_array(values, None, justify="left"))
         return header + result

pandas/io/formats/format.py

@@ -1215,18 +1215,16 @@ def _format_strings(self) -> list[str]:
 
         def _format(x):
             if self.na_rep is not None and is_scalar(x) and isna(x):
-                try:
-                    # try block for np.isnat specifically
-                    # determine na_rep if x is None or NaT-like
-                    if x is None:
-                        return "None"
-                    elif x is NA:
-                        return str(NA)
-                    elif x is NaT or np.isnat(x):
-                        return "NaT"
-                except (TypeError, ValueError):
-                    # np.isnat only handles datetime or timedelta objects
-                    pass
+                if x is None:
+                    return "None"
+                elif x is NA:
+                    return str(NA)
+                elif lib.is_float(x) and np.isinf(x):
+                    # TODO(3.0): this will be unreachable when use_inf_as_na
+                    #  deprecation is enforced
+                    return str(x)
+                elif x is NaT or isinstance(x, (np.datetime64, np.timedelta64)):
+                    return "NaT"
                 return self.na_rep
             elif isinstance(x, PandasObject):
                 return str(x)

pandas/tests/frame/test_repr_info.py

@@ -411,7 +411,7 @@ def test_to_records_with_na_record(self):
     def test_to_records_with_inf_as_na_record(self):
         # GH 48526
         expected = """   NaN  inf         record
-0  NaN    b    [0, inf, b]
+0  inf    b    [0, inf, b]
 1  NaN  NaN  [1, nan, nan]
 2    e    f      [2, e, f]"""
         msg = "use_inf_as_na option is deprecated"