to_html formatter not called for float values in a mixed-type column (2)

doc/source/whatsnew/v0.25.0.rst

@@ -347,6 +347,8 @@ I/O
 ^^^
 
 - Bug in :func:`DataFrame.to_html()` where values were truncated using display options instead of outputting the full content (:issue:`17004`)
+- Bug in :meth:`DataFrame.to_html` that would ignore ``formatters`` argument for float values in a column with ``dtype=object`` (:issue:`13021`)
+- Bug in :meth:`DataFrame.to_string` and :meth:`DataFrame.to_latex` that would add a leading space when using ``formatters`` on a column with ``dtype=object`` (:issue:`26002`)
 - Fixed bug in missing text when using :meth:`to_clipboard` if copying utf-16 characters in Python 3 on Windows (:issue:`25040`)
 - Bug in :func:`read_json` for ``orient='table'`` when it tries to infer dtypes by default, which is not applicable as dtypes are already defined in the JSON schema (:issue:`21345`)
 - Bug in :func:`read_json` for ``orient='table'`` and float index, as it infers index dtype by default, which is not applicable because index dtype is already defined in the JSON schema (:issue:`25433`)

pandas/io/formats/format.py

@@ -717,9 +717,11 @@ def _format_col(self, i):
         frame = self.tr_frame
         formatter = self._get_formatter(i)
         values_to_format = frame.iloc[:, i]._formatting_values()
+        shortcut = formatter is not None
         return format_array(values_to_format, formatter,
                             float_format=self.float_format, na_rep=self.na_rep,
-                            space=self.col_space, decimal=self.decimal)
+                            space=self.col_space, decimal=self.decimal,
+                            shortcut=shortcut)
 
     def to_html(self, classes=None, notebook=False, border=None):
         """
@@ -856,7 +858,7 @@ def _get_column_name_list(self):
 
 def format_array(values, formatter, float_format=None, na_rep='NaN',
                  digits=None, space=None, justify='right', decimal='.',
-                 leading_space=None):
+                 leading_space=None, shortcut=False):
     """
     Format an array for printing.
 
@@ -878,6 +880,9 @@ def format_array(values, formatter, float_format=None, na_rep='NaN',
         When formatting an Index subclass
         (e.g. IntervalIndex._format_native_types), we don't want the
         leading space since it should be left-aligned.
+    shortcut : bool, optional, default False
+        Whether to shortcut the formatting options. Used when specifying
+        custom formatters in to_string, to_latex and to_html
 
     Returns
     -------
@@ -911,7 +916,7 @@ def format_array(values, formatter, float_format=None, na_rep='NaN',
     fmt_obj = fmt_klass(values, digits=digits, na_rep=na_rep,
                         float_format=float_format, formatter=formatter,
                         space=space, justify=justify, decimal=decimal,
-                        leading_space=leading_space)
+                        leading_space=leading_space, shortcut=shortcut)
 
     return fmt_obj.get_result()
 
@@ -920,7 +925,8 @@ class GenericArrayFormatter(object):
 
     def __init__(self, values, digits=7, formatter=None, na_rep='NaN',
                  space=12, float_format=None, justify='right', decimal='.',
-                 quoting=None, fixed_width=True, leading_space=None):
+                 quoting=None, fixed_width=True, leading_space=None,
+                 shortcut=False):
         self.values = values
         self.digits = digits
         self.na_rep = na_rep
@@ -932,12 +938,17 @@ def __init__(self, values, digits=7, formatter=None, na_rep='NaN',
         self.quoting = quoting
         self.fixed_width = fixed_width
         self.leading_space = leading_space
+        self.shortcut = shortcut
 
     def get_result(self):
         fmt_values = self._format_strings()
         return _make_fixed_width(fmt_values, self.justify)
 
     def _format_strings(self):
+        # shortcut
+        if self.formatter is not None and self.shortcut:
+            return [self.formatter(x) for x in self.values]
+
         if self.float_format is None:
             float_format = get_option("display.float_format")
             if float_format is None:

pandas/tests/io/formats/data/html/gh13021_expected_output.html

@@ -0,0 +1,26 @@
+<table border="1" class="dataframe">
+  <thead>
+    <tr style="text-align: right;">
+      <th></th>
+      <th>x</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <th>0</th>
+      <td>a</td>
+    </tr>
+    <tr>
+      <th>1</th>
+      <td>$0</td>
+    </tr>
+    <tr>
+      <th>2</th>
+      <td>$10</td>
+    </tr>
+    <tr>
+      <th>3</th>
+      <td>$3</td>
+    </tr>
+  </tbody>
+</table>

pandas/tests/io/formats/test_format.py

@@ -511,10 +511,10 @@ def test_to_string_with_formatters(self):
                       ('object', lambda x: '-{x!s}-'.format(x=x))]
         result = df.to_string(formatters=dict(formatters))
         result2 = df.to_string(formatters=lzip(*formatters)[1])
-        assert result == ('  int  float    object\n'
-                          '0 0x1 [ 1.0]  -(1, 2)-\n'
-                          '1 0x2 [ 2.0]    -True-\n'
-                          '2 0x3 [ 3.0]   -False-')
+        assert result == ('  int  float   object\n'
+                          '0 0x1 [ 1.0] -(1, 2)-\n'
+                          '1 0x2 [ 2.0]   -True-\n'
+                          '2 0x3 [ 3.0]  -False-')
         assert result == result2
 
     def test_to_string_with_datetime64_monthformatter(self):

pandas/tests/io/formats/test_to_html.py

@@ -635,6 +635,17 @@ def test_to_html_invalid_classes_type(classes):
         df.to_html(classes=classes)
 
 
+def test_to_html_formatters_object_type(datapath):
+    # GH 13021
+    def f(x):
+        return x if isinstance(x, str) else '${:,.0f}'.format(x)
+
+    df = pd.DataFrame([['a'], [0], [10.4], [3]], columns=['x'])
+    result = df.to_html(formatters=dict(x=f))
+    expected = expected_html(datapath, 'gh13021_expected_output')
+    assert result == expected
+
+
 def test_to_html_round_column_headers():
     # GH 17280
     df = DataFrame([1], columns=[0.55555])

pandas/tests/io/formats/test_to_latex.py

@@ -125,11 +125,11 @@ def test_to_latex_with_formatters(self):
 
         expected = r"""\begin{tabular}{llrrl}
 \toprule
-{} & datetime64 &  float & int &    object \\
+{} & datetime64 &  float & int &   object \\
 \midrule
-index: 0 &    2016-01 & [ 1.0] & 0x1 &  -(1, 2)- \\
-index: 1 &    2016-02 & [ 2.0] & 0x2 &    -True- \\
-index: 2 &    2016-03 & [ 3.0] & 0x3 &   -False- \\
+index: 0 &    2016-01 & [ 1.0] & 0x1 & -(1, 2)- \\
+index: 1 &    2016-02 & [ 2.0] & 0x2 &   -True- \\
+index: 2 &    2016-03 & [ 3.0] & 0x3 &  -False- \\
 \bottomrule
 \end{tabular}
 """