scripts: Added punescape repetition + nesting

Maybe a bit overkill, but I needed more flexibility around adding
arbitrary whitespace.

New modifiers:

  %s                    A space
  %{                    Start a substring
  %}s                   End and format a subtring
  %aaa[mod]             Repeat this mod aaa times

With this, it's easy to add arbitrary spaces:

  "%8s" -> "        "

Or equivalently:

  "%8{ %}s" -> "        "

Which allows arbitrary repitition of any substring:

  "%4{hi!%}s" -> "hi!hi!hi!hi!"

This substring modifier includes its own format string, which allows for
some really nice padding normally impossible in printf:

  "%{%(a)d/%(b)d%}8s" % {a:1,b:2}   -> "     1/2"
  "%{%(a)d/%(b)d%}8s" % {a:12,b:34} -> "   12/34"

scripts/csv.py

@@ -1712,19 +1712,45 @@ def si2(x):
 # attrs can override __getitem__ for lazy attr generation
 def punescape(s, attrs=None):
     pattern = re.compile(
-        '%[%n]'
-            '|' '%x..'
-            '|' '%u....'
-            '|' '%U........'
-            '|' '%\((?P<field>[^)]*)\)'
-                '(?P<format>[+\- #0-9\.]*[siIdboxXfFeEgG])')
+        '%' '(?P<rep>[0-9]*)' '(?P<pun>'
+            '[%ns]'
+                '|' 'x..'
+                '|' 'u....'
+                '|' 'U........'
+                '|' '\((?P<field>[^)]*)\)'
+                    '(?P<format>[+\- #0-9\.]*[siIdboxXfFeEgG])'
+                '|' '\{(?P<substring>(?:[^%]|%[^}])*)%\}'
+                    '(?P<subformat>[+\- #0-9\.]*[siIdboxXfFeEgG])' ')')
+
+    def format(f, v):
+        if f[-1] in 'dboxX':
+            if isinstance(v, str):
+                v = dat(v, 0)
+            v = int(v)
+        elif f[-1] in 'iIfFeEgG':
+            if isinstance(v, str):
+                v = dat(v, 0)
+            v = float(v)
+            if f[-1] in 'iI':
+                v = (si if 'i' in f[-1] else si2)(v)
+                f = f.replace('i', 's').replace('I', 's')
+                if '+' in f and not v.startswith('-'):
+                    v = '+'+v
+                f = f.replace('+', '').replace('-', '')
+        else:
+            f = ('<' if '-' in f else '>') + f.replace('-', '')
+            v = str(v)
+        # note we need Python's new format syntax for binary
+        return ('{:%s}' % f).format(v)
+
     def unescape(m):
-        if m.group()[1] == '%': return '%'
-        elif m.group()[1] == 'n': return '\n'
-        elif m.group()[1] == 'x': return chr(int(m.group()[2:], 16))
-        elif m.group()[1] == 'u': return chr(int(m.group()[2:], 16))
-        elif m.group()[1] == 'U': return chr(int(m.group()[2:], 16))
-        elif m.group()[1] == '(':
+        if m.group('pun')[0] == '%':    s = '%'
+        elif m.group('pun')[0] == 'n':  s = '\n'
+        elif m.group('pun')[0] == 's':  s = ' '
+        elif m.group('pun')[0] == 'x':  s = chr(int(m.group('pun')[1:], 16))
+        elif m.group('pun')[0] == 'u':  s = chr(int(m.group('pun')[1:], 16))
+        elif m.group('pun')[0] == 'U':  s = chr(int(m.group('pun')[1:], 16))
+        elif m.group('pun')[0] == '(':
             if attrs is not None:
                 try:
                     v = attrs[m.group('field')]
@@ -1732,27 +1758,17 @@ def punescape(s, attrs=None):
                     return m.group()
             else:
                 return m.group()
-            f = m.group('format')
-            if f[-1] in 'dboxX':
-                if isinstance(v, str):
-                    v = dat(v, 0)
-                v = int(v)
-            elif f[-1] in 'iIfFeEgG':
-                if isinstance(v, str):
-                    v = dat(v, 0)
-                v = float(v)
-                if f[-1] in 'iI':
-                    v = (si if 'i' in f[-1] else si2)(v)
-                    f = f.replace('i', 's').replace('I', 's')
-                    if '+' in f and not v.startswith('-'):
-                        v = '+'+v
-                    f = f.replace('+', '').replace('-', '')
-            else:
-                f = ('<' if '-' in f else '>') + f.replace('-', '')
-                v = str(v)
-            # note we need Python's new format syntax for binary
-            return ('{:%s}' % f).format(v)
-        else: assert False
+            s = format(m.group('format'), v)
+        elif m.group('pun')[0] == '{':
+            v = punescape(m.group('substring'), attrs)
+            s = format(m.group('subformat'), v)
+        else:
+            return m.group()
+
+        if m.group('rep'):
+            s = int(m.group('rep'), 10) * s
+
+        return s
 
     return re.sub(pattern, unescape, s)
 
@@ -1769,6 +1785,7 @@ def punescape_help():
     print('mods:')
     print('  %-21s %s' % ('%%', 'A literal % character'))
     print('  %-21s %s' % ('%n', 'A newline'))
+    print('  %-21s %s' % ('%s', 'A space'))
     print('  %-21s %s' % (
             '%xaa', 'A character with the hex value aa'))
     print('  %-21s %s' % (
@@ -1785,6 +1802,12 @@ def punescape_help():
             '%(field)[dboxX]', 'An existing field formatted as an integer'))
     print('  %-21s %s' % (
             '%(field)[fFeEgG]', 'An existing field formatted as a float'))
+    print('  %-21s %s' % (
+            '%{', 'Start a substring'))
+    print('  %-21s %s' % (
+            '%}s', 'End and format a subtring'))
+    print('  %-21s %s' % (
+            '%aaa[mod]', 'Repeat this mod aaa times'))
 
 
 # open with '-' for stdin/stdout