diff -r d083b6ead156 Lib/base64.py
--- a/Lib/base64.py	Mon Mar 10 11:05:07 2014 +0100
+++ b/Lib/base64.py	Mon Mar 10 11:37:38 2014 +0100
@@ -274,10 +274,23 @@ def b16decode(s, casefold=False):
 # Ascii85 encoding/decoding
 #
 
+_a85chars = None
+_a85chars2 = None
+_A85START = b"<~"
+_A85END = b"~>"
+
+def _init_a85_tables():
+    """Precompute tables for faster ascii85 codec."""
+    global _a85chars, _a85chars2
+    if _a85chars is None:
+        _a85chars = [bytes([i]) for i in range(33, 118)]
+        _a85chars2 = [(a + b) for a in _a85chars for b in _a85chars]
+
 def _85encode(b, chars, chars2, pad=False, foldnuls=False, foldspaces=False):
     # Helper function for a85encode and b85encode
     if not isinstance(b, bytes_types):
         b = memoryview(b).tobytes()
+    _init_a85_tables()
 
     padding = (-len(b)) % 4
     if padding:
@@ -300,11 +313,6 @@ def _85encode(b, chars, chars2, pad=Fals
 
     return b''.join(chunks)
 
-_A85START = b"<~"
-_A85END = b"~>"
-_a85chars = [bytes([i]) for i in range(33, 118)]
-_a85chars2 = [(a + b) for a in _a85chars for b in _a85chars]
-
 def a85encode(b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False):
     """Encode a byte string using Ascii85.
 
@@ -324,6 +332,7 @@ def a85encode(b, *, foldspaces=False, wr
     adobe controls whether the encoded byte sequence is framed with <~ and ~>,
     which is used by the Adobe implementation.
     """
+    _init_a85_tables()
     result = _85encode(b, _a85chars, _a85chars2, pad, True, foldspaces)
 
     if adobe:
@@ -408,23 +417,33 @@ def a85decode(b, *, foldspaces=False, ad
 
 # The following code is originally taken (with permission) from Mercurial
 
-_b85chars = b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
-            b"abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~"
-_b85chars = [bytes([i]) for i in _b85chars]
-_b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]
+_b85chars = None
+_b85chars2 = None
 _b85dec = None
 
+def _init_b85_tables():
+    """Precompute tables for faster base85 codec."""
+    global _b85chars, _b85chars2
+    if _b85chars is None:
+        _b85chars = b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
+                    b"abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~"
+        _b85chars = [bytes([i]) for i in _b85chars]
+        _b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]
+
 def b85encode(b, pad=False):
     """Encode an ASCII-encoded byte array in base85 format.
 
     If pad is true, the input is padded with "\0" so its length is a multiple of
     4 characters before encoding.
     """
+    _init_b85_tables()
     return _85encode(b, _b85chars, _b85chars2, pad)
 
 def b85decode(b):
     """Decode base85-encoded byte array"""
     b = _bytes_from_decode_data(b)
+    _init_b85_tables()
+
     global _b85dec
     if _b85dec is None:
         _b85dec = [None] * 256