Merge pull request #183 from myheroyuki/Add_header_alignment_attribute

Add header alignment attribute

README.md

@@ -295,6 +295,20 @@ gives:
 +-----------+------+------------+-----------------+
 ```
 
+##### Other alignment
+
+You can also change the alignment of the headers of the columns using the `header_align`
+attribute in the same way as the `align` attribute.
+
+```python
+x.header_align["City name"] = "l"
+print(x)
+```
+
+The `valign` attribute works in the same way as the other align attributes for
+controlling vertical alignment. It accepts the values `"t"`, `"m"` and `"b"` for top,
+middle, and bottom respectively.
+
 ##### Sorting your table by a field
 
 You can make sure that your ASCII tables are produced with the data sorted by one

src/prettytable/prettytable.py

@@ -135,6 +135,7 @@ def __init__(self, field_names=None, **kwargs):
         self._rows = []
         self.align = {}
         self.valign = {}
+        self.header_align = {}
         self.max_width = {}
         self.min_width = {}
         self.int_format = {}
@@ -189,6 +190,7 @@ def __init__(self, field_names=None, **kwargs):
             "bottom_left_junction_char",
             "align",
             "valign",
+            "header_align",
             "max_width",
             "min_width",
             "none_format",
@@ -231,6 +233,7 @@ def __init__(self, field_names=None, **kwargs):
         # Column specific arguments, use property.setters
         self.align = kwargs["align"] or {}
         self.valign = kwargs["valign"] or {}
+        self.header_align = kwargs["header_align"] or {}
         self.max_width = kwargs["max_width"] or {}
         self.min_width = kwargs["min_width"] or {}
         self.int_format = kwargs["int_format"] or {}
@@ -615,6 +618,15 @@ def field_names(self, val):
                 self._align[field_name] = self._align[BASE_ALIGN_VALUE]
         else:
             self.align = "c"
+        if self._header_align and old_names:
+            for old_name, new_name in zip(old_names, val):
+                self._header_align[new_name] = self._header_align[old_name]
+            for old_name in old_names:
+                if old_name in self._header_align and old_name not in val:
+                    self._header_align.pop(old_name)
+        elif self._header_align:
+            for field_name in self._field_names:
+                self._header_align[field_name] = self._header_align[BASE_ALIGN_VALUE]
         if self._valign and old_names:
             for old_name, new_name in zip(old_names, val):
                 self._valign[new_name] = self._valign[old_name]
@@ -648,6 +660,30 @@ def align(self, val):
                 for field in self._field_names:
                     self._align[field] = val
 
+    @property
+    def header_align(self):
+        """Controls alignment of header fields
+        Arguments:
+
+        header_align - header alignment, one of "l", "c", or "r" """
+        return self._header_align
+
+    @header_align.setter
+    def header_align(self, val):
+        if val is None or (isinstance(val, dict) and len(val) == 0):
+            if not self._field_names:
+                self._header_align = {BASE_ALIGN_VALUE: "c"}
+            else:
+                for field in self._field_names:
+                    self._header_align[field] = "c"
+        else:
+            self._validate_align(val)
+            if not self._field_names:
+                self._header_align = {BASE_ALIGN_VALUE: val}
+            else:
+                for field in self._field_names:
+                    self._header_align[field] = val
+
     @property
     def valign(self):
         """Controls vertical alignment of fields
@@ -1428,7 +1464,7 @@ def del_row(self, row_index):
             )
         del self._rows[row_index]
 
-    def add_column(self, fieldname, column, align="c", valign="t"):
+    def add_column(self, fieldname, column, align="c", valign="t", header_align="c"):
 
         """Add a column to the table.
 
@@ -1444,10 +1480,12 @@ def add_column(self, fieldname, column, align="c", valign="t"):
 
         if len(self._rows) in (0, len(column)):
             self._validate_align(align)
+            self._validate_align(header_align)
             self._validate_valign(valign)
             self._field_names.append(fieldname)
             self._align[fieldname] = align
             self._valign[fieldname] = valign
+            self._header_align[fieldname] = header_align
             for i in range(0, len(column)):
                 if len(self._rows) < i + 1:
                     self._rows.append([])
@@ -1465,6 +1503,7 @@ def add_autoindex(self, fieldname="Index"):
         self._field_names.insert(0, fieldname)
         self._align[fieldname] = self.align
         self._valign[fieldname] = self.valign
+        self._header_align[fieldname] = self.header_align
         for i, row in enumerate(self._rows):
             row.insert(0, i + 1)
 
@@ -1850,15 +1889,14 @@ def _stringify_header(self, options):
                 fieldname = fieldname[:width]
             bits.append(
                 " " * lpad
-                + self._justify(fieldname, width, self._align[field])
+                + self._justify(fieldname, width, self._header_align[field])
                 + " " * rpad
             )
             if options["border"] or options["preserve_internal_border"]:
                 if options["vrules"] == ALL:
                     bits.append(options["vertical_char"])
                 else:
                     bits.append(" ")
-
         # If only preserve_internal_border is true, then we just appended
         # a vertical character at the end when we wanted a space
         if not options["border"] and options["preserve_internal_border"]:
@@ -2178,8 +2216,15 @@ def _get_formatted_html_string(self, options):
                 if options["fields"] and field not in options["fields"]:
                     continue
                 lines.append(
-                    '            <th style="padding-left: %dem; padding-right: %dem; text-align: center">%s</th>'  # noqa: E501
-                    % (lpad, rpad, escape(field).replace("\n", linebreak))
+                    '            <th style="padding-left: %dem; padding-right: %dem; text-align: %s">%s</th>'  # noqa: E501
+                    % (
+                        lpad,
+                        rpad,
+                        {"l": "left", "r": "right", "c": "center"}[
+                            self._header_align[field]
+                        ],
+                        escape(field).replace("\n", linebreak),
+                    )  # noqa: E501
                 )
             lines.append("        </tr>")
             lines.append("    </thead>")

tests/test_prettytable.py

@@ -331,6 +331,7 @@ def test_add_field_names_later(self, field_name_less_table: prettytable):
 def aligned_before_table():
     x = PrettyTable()
     x.align = "r"
+    x.header_align = "r"
     x.field_names = ["City name", "Area", "Population", "Annual Rainfall"]
     x.add_row(["Adelaide", 1295, 1158259, 600.5])
     x.add_row(["Brisbane", 5905, 1857594, 1146.4])
@@ -354,6 +355,7 @@ def aligned_after_table():
     x.add_row(["Melbourne", 1566, 3806092, 646.9])
     x.add_row(["Perth", 5386, 1554769, 869.4])
     x.align = "r"
+    x.header_align = "r"
     return x
 
 
@@ -1435,6 +1437,41 @@ def test_style_align(self, style, expected):
         result = t.get_string()
         assert result.strip() == expected.strip()
 
+    @pytest.mark.parametrize(
+        "style, expected",
+        [
+            pytest.param(
+                DEFAULT,
+                """
++---------+--------+--------+
+| L       |   C    |      R |
++---------+--------+--------+
+| value 1 | value2 | value3 |
+| value 4 | value5 | value6 |
+| value 7 | value8 | value9 |
++---------+--------+--------+
+""",
+                id="MARKDOWN",
+            ),
+        ],
+    )
+    def test_style_header_align(self, style, expected):
+        # Arrange
+        t = helper_table()
+        t.field_names = ["L", "C", "R"]
+
+        assert t.header_align["L"] == "c"
+
+        # Act
+        t.set_style(style)
+        t.header_align["L"] = "l"
+        t.header_align["C"] = "c"
+        t.header_align["R"] = "r"
+
+        # Assert
+        result = t.get_string()
+        assert result.strip() == expected.strip()
+
 
 class TestCsvOutput:
     def test_csv_output(self):