rf(cmdline): Simplify table2string implementation

The previous table2string implementation reimplemented Python
formatting, calculating spaces for aligning left, right or center. This
patch just translates our mini-language into the Python mini-language,
and updates the tests.

Previously, when centering required adding an odd number of spaces, we
added the extra to the left, while Python adds to the right.
This difference does not seem worth preserving.

This also avoids allocating a numpy array in order to transpose by using
the `zip(*list)` trick.

Author: effigies

nibabel/cmdline/tests/test_utils.py

@@ -28,17 +28,37 @@
 
 
 def test_table2string():
-    assert table2string([['A', 'B', 'C', 'D'], ['E', 'F', 'G', 'H']]) == 'A B C D\nE F G H\n'
+    # Trivial case should do something sensible
+    assert table2string([]) == '\n'
     assert (
         table2string(
-            [
-                ["Let's", 'Make', 'Tests', 'And'],
-                ['Have', 'Lots', 'Of', 'Fun'],
-                ['With', 'Python', 'Guys', '!'],
-            ]
+            [['A', 'B', 'C', 'D'],
+             ['E', 'F', 'G', 'H']]
+        ) == (
+            'A B C D\n'
+            'E F G H\n'
         )
-        == "Let's  Make  Tests And\n Have  Lots    Of  Fun" + '\n With Python  Guys  !\n'
-    )
+    )  # fmt: skip
+    assert (
+        table2string(
+            [["Let's", 'Make', 'Tests', 'And'],
+             ['Have', 'Lots', 'Of', 'Fun'],
+             ['With', 'Python', 'Guys', '!']]
+        ) == (
+            "Let's  Make  Tests And\n"
+            'Have   Lots   Of   Fun\n'
+            'With  Python Guys   !\n'
+        )
+    )  # fmt: skip
+    assert (
+        table2string(
+            [['This', 'Table', '@lIs', 'Ragged'],
+             ['And', '@rit', 'uses', '@csome', 'alignment', 'markup']]
+        ) == (
+            'This Table Is   Ragged\n'
+            'And     it uses  some  alignment markup\n'
+        )
+    )  # fmt: skip
 
 
 def test_ap():

nibabel/cmdline/utils.py

@@ -12,10 +12,6 @@
 
 # global verbosity switch
 import re
-from io import StringIO
-from math import ceil
-
-import numpy as np
 
 verbose_level = 0
 
@@ -42,32 +38,28 @@ def table2string(table, out=None):
     table : list of lists of strings
       What is aimed to be printed
     out : None or stream
-      Where to print. If None -- will print and return string
+      Where to print. If None, return string
 
     Returns
     -------
     string if out was None
     """
 
-    print2string = out is None
-    if print2string:
-        out = StringIO()
-
     # equalize number of elements in each row
     nelements_max = len(table) and max(len(x) for x in table)
 
+    table = [row + [''] * (nelements_max - len(row)) for row in table]
     for i, table_ in enumerate(table):
         table[i] += [''] * (nelements_max - len(table_))
 
-    # figure out lengths within each column
-    atable = np.asarray(table)
     # eat whole entry while computing width for @w (for wide)
     markup_strip = re.compile('^@([lrc]|w.*)')
-    col_width = [max(len(markup_strip.sub('', x)) for x in column) for column in atable.T]
-    string = ''
-    for i, table_ in enumerate(table):
-        string_ = ''
-        for j, item in enumerate(table_):
+    col_width = [max(len(markup_strip.sub('', x)) for x in column) for column in zip(*table)]
+    trans = str.maketrans("lrcw", "<>^^")
+    lines = []
+    for row in table:
+        line = []
+        for item, width in zip(row, col_width):
             item = str(item)
             if item.startswith('@'):
                 align = item[1]
@@ -77,26 +69,14 @@ def table2string(table, out=None):
             else:
                 align = 'c'
 
-            nspacesl = max(ceil((col_width[j] - len(item)) / 2.0), 0)
-            nspacesr = max(col_width[j] - nspacesl - len(item), 0)
-
-            if align in ('w', 'c'):
-                pass
-            elif align == 'l':
-                nspacesl, nspacesr = 0, nspacesl + nspacesr
-            elif align == 'r':
-                nspacesl, nspacesr = nspacesl + nspacesr, 0
-            else:
-                raise RuntimeError(f'Should not get here with align={align}')
-
-            string_ += '%%%ds%%s%%%ds ' % (nspacesl, nspacesr) % ('', item, '')
-        string += string_.rstrip() + '\n'
-    out.write(string)
+            line.append(f'{item:{align.translate(trans)}{width}}')
+        lines.append(' '.join(line).rstrip())
 
-    if print2string:
-        value = out.getvalue()
-        out.close()
-        return value
+    ret = '\n'.join(lines) + '\n'
+    if out is not None:
+        out.write(ret)
+    else:
+        return ret
 
 
 def ap(helplist, format_, sep=', '):