Make DataFrame.to_string output full content by default (#28052)

Author: Luke Shepard

doc/source/user_guide/options.rst

@@ -353,7 +353,7 @@ display.max_colwidth                    50           The maximum width in charac
                                                      a column in the repr of a pandas
                                                      data structure. When the column overflows,
                                                      a "..." placeholder is embedded in
-                                                     the output.
+                                                     the output. 'None' value means unlimited.
 display.max_info_columns                100          max_info_columns is used in DataFrame.info
                                                      method to decide if per column information
                                                      will be printed.

doc/source/whatsnew/v1.0.0.rst

@@ -21,6 +21,8 @@ including other versions of pandas.
 Enhancements
 ~~~~~~~~~~~~
 
+- :meth:`DataFrame.to_string` added the ``max_colwidth`` parameter to control when wide columns are truncated (:issue:`9784`)
+-
 
 .. _whatsnew_1000.enhancements.other:
 
@@ -191,6 +193,7 @@ I/O
 - Bug in :meth:`DataFrame.to_json` where using a Tuple as a column or index value and using ``orient="columns"`` or ``orient="index"`` would produce invalid JSON (:issue:`20500`)
 - Improve infinity parsing. :meth:`read_csv` now interprets ``Infinity``, ``+Infinity``, ``-Infinity`` as floating point values (:issue:`10065`)
 - Bug in :meth:`DataFrame.to_csv` where values were truncated when the length of ``na_rep`` was shorter than the text input data. (:issue:`25099`)
+- Bug in :func:`DataFrame.to_string` where values were truncated using display options instead of outputting the full content (:issue:`9784`)
 
 Plotting
 ^^^^^^^^

pandas/core/config_init.py

@@ -148,10 +148,10 @@ def use_numexpr_cb(key):
 """
 
 max_colwidth_doc = """
-: int
+: int or None
     The maximum width in characters of a column in the repr of
     a pandas data structure. When the column overflows, a "..."
-    placeholder is embedded in the output.
+    placeholder is embedded in the output. A 'None' value means unlimited.
 """
 
 colheader_justify_doc = """
@@ -340,7 +340,9 @@ def is_terminal():
         validator=is_instance_factory([type(None), int]),
     )
     cf.register_option("max_categories", 8, pc_max_categories_doc, validator=is_int)
-    cf.register_option("max_colwidth", 50, max_colwidth_doc, validator=is_int)
+    cf.register_option(
+        "max_colwidth", 50, max_colwidth_doc, validator=is_nonnegative_int
+    )
     if is_terminal():
         max_cols = 0  # automatically determine optimal number of columns
     else:

pandas/core/frame.py

@@ -641,6 +641,7 @@ def __repr__(self):
         max_rows = get_option("display.max_rows")
         min_rows = get_option("display.min_rows")
         max_cols = get_option("display.max_columns")
+        max_colwidth = get_option("display.max_colwidth")
         show_dimensions = get_option("display.show_dimensions")
         if get_option("display.expand_frame_repr"):
             width, _ = console.get_console_size()
@@ -652,6 +653,7 @@ def __repr__(self):
             min_rows=min_rows,
             max_cols=max_cols,
             line_width=width,
+            max_colwidth=max_colwidth,
             show_dimensions=show_dimensions,
         )
 
@@ -730,12 +732,17 @@ def to_string(
         show_dimensions=False,
         decimal=".",
         line_width=None,
+        max_colwidth=None,
     ):
         """
         Render a DataFrame to a console-friendly tabular output.
         %(shared_params)s
         line_width : int, optional
             Width to wrap a line in characters.
+        max_colwidth : int, optional
+            Max width to truncate each column in characters. By default, no limit.
+
+            .. versionadded:: 1.0.0
         %(returns)s
         See Also
         --------
@@ -752,26 +759,29 @@ def to_string(
         2     3     6
         """
 
-        formatter = fmt.DataFrameFormatter(
-            self,
-            columns=columns,
-            col_space=col_space,
-            na_rep=na_rep,
-            formatters=formatters,
-            float_format=float_format,
-            sparsify=sparsify,
-            justify=justify,
-            index_names=index_names,
-            header=header,
-            index=index,
-            min_rows=min_rows,
-            max_rows=max_rows,
-            max_cols=max_cols,
-            show_dimensions=show_dimensions,
-            decimal=decimal,
-            line_width=line_width,
-        )
-        return formatter.to_string(buf=buf)
+        from pandas import option_context
+
+        with option_context("display.max_colwidth", max_colwidth):
+            formatter = fmt.DataFrameFormatter(
+                self,
+                columns=columns,
+                col_space=col_space,
+                na_rep=na_rep,
+                formatters=formatters,
+                float_format=float_format,
+                sparsify=sparsify,
+                justify=justify,
+                index_names=index_names,
+                header=header,
+                index=index,
+                min_rows=min_rows,
+                max_rows=max_rows,
+                max_cols=max_cols,
+                show_dimensions=show_dimensions,
+                decimal=decimal,
+                line_width=line_width,
+            )
+            return formatter.to_string(buf=buf)
 
     # ----------------------------------------------------------------------
 

pandas/io/clipboards.py

@@ -131,7 +131,7 @@ def to_clipboard(obj, excel=True, sep=None, **kwargs):  # pragma: no cover
 
     if isinstance(obj, ABCDataFrame):
         # str(df) has various unhelpful defaults, like truncation
-        with option_context("display.max_colwidth", 999999):
+        with option_context("display.max_colwidth", None):
             objstr = obj.to_string(**kwargs)
     else:
         objstr = str(obj)

pandas/io/formats/html.py

@@ -377,7 +377,7 @@ def _write_header(self, indent: int) -> None:
         self.write("</thead>", indent)
 
     def _get_formatted_values(self) -> Dict[int, List[str]]:
-        with option_context("display.max_colwidth", 999999):
+        with option_context("display.max_colwidth", None):
             fmt_values = {i: self.fmt._format_col(i) for i in range(self.ncols)}
         return fmt_values
 

pandas/tests/config/test_config.py

@@ -218,6 +218,7 @@ def test_validation(self):
         self.cf.set_option("a", 2)  # int is_int
         self.cf.set_option("b.c", "wurld")  # str is_str
         self.cf.set_option("d", 2)
+        self.cf.set_option("d", None)  # non-negative int can be None
 
         # None not is_int
         with pytest.raises(ValueError, match=msg):

pandas/tests/io/formats/test_format.py

@@ -527,6 +527,45 @@ def test_str_max_colwidth(self):
                 "1  foo  bar                stuff  1"
             )
 
+    def test_to_string_truncate(self):
+        # GH 9784 - dont truncate when calling DataFrame.to_string
+        df = pd.DataFrame(
+            [
+                {
+                    "a": "foo",
+                    "b": "bar",
+                    "c": "let's make this a very VERY long line that is longer "
+                    "than the default 50 character limit",
+                    "d": 1,
+                },
+                {"a": "foo", "b": "bar", "c": "stuff", "d": 1},
+            ]
+        )
+        df.set_index(["a", "b", "c"])
+        assert df.to_string() == (
+            "     a    b                                         "
+            "                                                c  d\n"
+            "0  foo  bar  let's make this a very VERY long line t"
+            "hat is longer than the default 50 character limit  1\n"
+            "1  foo  bar                                         "
+            "                                            stuff  1"
+        )
+        with option_context("max_colwidth", 20):
+            # the display option has no effect on the to_string method
+            assert df.to_string() == (
+                "     a    b                                         "
+                "                                                c  d\n"
+                "0  foo  bar  let's make this a very VERY long line t"
+                "hat is longer than the default 50 character limit  1\n"
+                "1  foo  bar                                         "
+                "                                            stuff  1"
+            )
+        assert df.to_string(max_colwidth=20) == (
+            "     a    b                    c  d\n"
+            "0  foo  bar  let's make this ...  1\n"
+            "1  foo  bar                stuff  1"
+        )
+
     def test_auto_detect(self):
         term_width, term_height = get_terminal_size()
         fac = 1.05  # Arbitrary large factor to exceed term width