bpo-32820: __format__ method for ipaddress

Lib/ipaddress.py

@@ -1089,6 +1089,43 @@ class _BaseV4:
  def _explode_shorthand_ip_string(self):
  return str(self)
 
+ def __format__(self, fmt):
+ """Format: ends with b for bin, h for hex, n for native (bin for ipv4,
+ hex for ipv6). Takes # to include 0b, and _ as a separator
+ """
+ if len(fmt) and fmt[-1] in 'bnx':
+ fmt_base = fmt[-1]
+ if fmt_base == 'n':
+ fmt_base = 'b' # binary is default for ipv4
+
+ if '_' in fmt:
+ separator = '_'
+ else:
+ separator = ''
+
+ # binary
+ if fmt_base == 'b':
+ # resulting string is '0b' + 32 bits
+ # plus 7 _ if needed
+ padlen = IPV4LENGTH+2 + (7*len(separator))
+
+ # hex
+ elif fmt_base == 'x':
+ # resulting string is '0x' + 8 hex digits
+ # plus a single _ if needed
+ padlen = int(IPV4LENGTH/4)+2 + len(separator)
+
+ retstr = f'{int(self):#0{padlen}{separator}{fmt_base}}'
+
+ # strip left two if necessary
+ if '#' not in fmt:
+ retstr = retstr[2:]
+
+ else:
+ retstr = str(self)
+
+ return retstr
+
  @classmethod
  def _make_netmask(cls, arg):
  """Make a (netmask, prefix_len) tuple from the given argument.
@@ -1627,6 +1664,43 @@ class _BaseV6:
  # when constructed (see _make_netmask()).
  _netmask_cache = {}
 
+ def __format__(self, fmt):
+ """Format: ends with b for bin, h for hex, n for native (bin for ipv4,
+ hex for ipv6). Takes # to include 0b, and _ as a separator
+ """
+ if len(fmt) and fmt[-1] in 'bnx':
+ fmt_base = fmt[-1]
+ if fmt_base == 'n':
+ fmt_base = 'x' # hex is default for ipv4
+
+ if '_' in fmt:
+ separator = '_'
+ else:
+ separator = ''
+
+ # binary
+ if fmt_base == 'b':
+ # resulting string is '0b' + 32 bits
+ # plus 7 _ if needed
+ padlen = IPV6LENGTH+2 + (31*len(separator))
+
+ # hex
+ elif fmt_base == 'x':
+ # resulting string is '0x' + 8 hex digits
+ # plus 7 single _ if needed
+ padlen = int(IPV6LENGTH/4)+2 + (7*len(separator))
+
+ retstr = f'{int(self):#0{padlen}{separator}{fmt_base}}'
+
+ # strip left two if necessary
+ if '#' not in fmt:
+ retstr = retstr[2:]
+
+ else:
+ retstr = str(self)
+
+ return retstr
+
  @classmethod
  def _make_netmask(cls, arg):
  """Make a (netmask, prefix_len) tuple from the given argument.

Lib/test/test_ipaddress.py

@@ -170,6 +170,27 @@ def assertBadLength(length):
 class AddressTestCase_v4(BaseTestCase, CommonTestMixin_v4):
  factory = ipaddress.IPv4Address
 
+ def test_format(self):
+ addr = ipaddress.IPv4Address("1.2.3.4")
+ pairs = [
+ ("b" ,"00000001000000100000001100000100"),
+ ("n" ,"00000001000000100000001100000100"),
+ ("x" ,"01020304"),
+ ("_b" ,"0000_0001_0000_0010_0000_0011_0000_0100"),
+ ("_n" ,"0000_0001_0000_0010_0000_0011_0000_0100"),
+ ("_x" ,"0102_0304"),
+ ("#b" ,"0b00000001000000100000001100000100"),
+ ("#n" ,"0b00000001000000100000001100000100"),
+ ("#x" ,"0x01020304"),
+ ("#_b" ,"0b0000_0001_0000_0010_0000_0011_0000_0100"),
+ ("#_n" ,"0b0000_0001_0000_0010_0000_0011_0000_0100"),
+ ("#_x" ,"0x0102_0304"),
+ ]
+ for (fmt, txt) in pairs:
+ res = format(addr, fmt)
+ self.assertEqual(txt, format(addr, fmt))
+
+
  def test_network_passed_as_address(self):
  addr = "127.0.0.1/24"
  with self.assertAddressError("Unexpected '/' in %r", addr):
@@ -266,6 +287,41 @@ def test_weakref(self):
 class AddressTestCase_v6(BaseTestCase, CommonTestMixin_v6):
  factory = ipaddress.IPv6Address
 
+ def test_format(self):
+ addr = ipaddress.IPv6Address("::1.2.3.4")
+ pairs = [
+ ("b"
+ ,"000000000000000000000000000000000"
+ "000000000000000000000000000000000"
+ "00000000000000000000000000000000"
+ "000001000000100000001100000100"),
+ ("n" ,"00000000000000000000000001020304"),
+ ("x" ,"00000000000000000000000001020304"),
+ ("_b"
+ ,"0000_0000_0000_0000_0000_0000_0000_0000_"
+ "0000_0000_0000_0000_0000_0000_0000_0000_"
+ "0000_0000_0000_0000_0000_0000_0000_0000_"
+ "0000_0001_0000_0010_0000_0011_0000_0100"),
+ ("_n" ,"0000_0000_0000_0000_0000_0000_0102_0304"),
+ ("_x" ,"0000_0000_0000_0000_0000_0000_0102_0304"),
+ ("#b"
+ ,"0b000000000000000000000000000000000"
+ "000000000000000000000000000000000"
+ "000000000000000000000000000000000"
+ "00001000000100000001100000100"),
+ ("#n" ,"0x00000000000000000000000001020304"),
+ ("#x" ,"0x00000000000000000000000001020304"),
+ ("#_b"
+ ,"0b0000_0000_0000_0000_0000_0000_0000_0000_"
+ "0000_0000_0000_0000_0000_0000_0000_0000_"
+ "0000_0000_0000_0000_0000_0000_0000_0000_"
+ "0000_0001_0000_0010_0000_0011_0000_0100"),
+ ("#_n" ,"0x0000_0000_0000_0000_0000_0000_0102_0304"),
+ ("#_x" ,"0x0000_0000_0000_0000_0000_0000_0102_0304"),
+ ]
+ for (fmt, txt) in pairs:
+ res = format(addr, fmt)
+
  def test_network_passed_as_address(self):
  addr = "::1/24"
  with self.assertAddressError("Unexpected '/' in %r", addr):

Misc/NEWS.d/next/Library/2018-02-13-12-25-43.bpo-32820.0stF0u.rst

@@ -0,0 +1,4 @@
+Added __format__ to IPv4 and IPv6 classes. Always outputs a fully zero-
+padded string. Supports b/x/n modifiers (bin/hex/native format). Native
+format for IPv4 is bin, native format for IPv6 is hex. Also supports '#' and
+'_' modifiers.