python · serhiy-storchaka · Dec 25, 2025 · Dec 23, 2025
diff --git a/Doc/library/base64.rst b/Doc/library/base64.rst
@@ -267,14 +267,20 @@ Refer to the documentation of the individual functions for more information.
   .. versionadded:: 3.4


-.. function:: z85encode(s)
+.. function:: z85encode(s, pad=False)

   Encode the :term:`bytes-like object` *s* using Z85 (as used in ZeroMQ)
   and return the encoded :class:`bytes`.  See `Z85  specification
   <https://rfc.zeromq.org/spec/32/>`_ for more information.

+   If *pad* is true, the input is padded with ``b'\0'`` so its length is a
+   multiple of 4 bytes before encoding.
+
   .. versionadded:: 3.13

+   .. versionchanged:: next
+      The *pad* parameter was added.
+

 .. function:: z85decode(s)


diff --git a/Lib/base64.py b/Lib/base64.py
@@ -508,9 +508,9 @@ def b85decode(b):
 )
 _z85_encode_translation = bytes.maketrans(_b85alphabet, _z85alphabet)

-def z85encode(s):
+def z85encode(s, pad=False):
    """Encode bytes-like object b in z85 format and return a bytes object."""
-    return b85encode(s).translate(_z85_encode_translation)
+    return b85encode(s, pad).translate(_z85_encode_translation)

 def z85decode(s):
    """Decode the z85-encoded bytes-like object or ASCII string b

diff --git a/Lib/test/test_base64.py b/Lib/test/test_base64.py
@@ -665,6 +665,7 @@ def test_z85encode(self):

        tests = {
            b'': b'',
+            b'\x86\x4F\xD2\x6F\xB5\x59\xF7\x5B': b'HelloWorld',
            b'www.python.org': b'CxXl-AcVLsz/dgCA+t',
            bytes(range(255)): b"""009c61o!#m2NH?C3>iWS5d]J*6CRx17-skh9337x"""
                b"""ar.{NbQB=+c[cR@eg&FcfFLssg=mfIi5%2YjuU>)kTv.7l}6Nnnj=AD"""
@@ -840,6 +841,21 @@ def test_b85_padding(self):
        eq(base64.b85decode(b'czAet'), b"xxxx")
        eq(base64.b85decode(b'czAetcmMzZ'), b"xxxxx\x00\x00\x00")

+    def test_z85_padding(self):
+        eq = self.assertEqual
+
+        eq(base64.z85encode(b"x", pad=True), b'CMmZz')
+        eq(base64.z85encode(b"xx", pad=True), b'CZ6h*')
+        eq(base64.z85encode(b"xxx", pad=True), b'CZaDk')
+        eq(base64.z85encode(b"xxxx", pad=True), b'CZaET')
+        eq(base64.z85encode(b"xxxxx", pad=True), b'CZaETCMmZz')
+
+        eq(base64.z85decode(b'CMmZz'), b"x\x00\x00\x00")
+        eq(base64.z85decode(b'CZ6h*'), b"xx\x00\x00")
+        eq(base64.z85decode(b'CZaDk'), b"xxx\x00")
+        eq(base64.z85decode(b'CZaET'), b"xxxx")
+        eq(base64.z85decode(b'CZaETCMmZz'), b"xxxxx\x00\x00\x00")
+
    def test_a85decode_errors(self):
        illegal = (set(range(32)) | set(range(118, 256))) - set(b' \t\n\r\v')
        for c in illegal:

diff --git a/Misc/ACKS b/Misc/ACKS
@@ -418,6 +418,7 @@ Lisandro Dalcin
 Darren Dale
 Andrew Dalke
 Lars Damerow
+Hauke Dämpfling
 Evan Dandrea
 Eric Daniel
 Scott David Daniels

diff --git a/Misc/NEWS.d/next/Library/2025-12-23-17-07-22.gh-issue-143103.LRjXEW.rst b/Misc/NEWS.d/next/Library/2025-12-23-17-07-22.gh-issue-143103.LRjXEW.rst
@@ -0,0 +1 @@
+Add padding support to :func:`base64.z85encode` via the ``pad`` parameter.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Add padding support to :func:`base64.z85encode` via the ``pad`` parameter.