Does python provide a list of special characters for uuencoding?

Question

I can find the uuencode character mappings on wikipedia. Does python have a means to loop through this list?

for x in [builtin_uuencode_mappings]:
    print(x)

I would like to focus on special characters such as "!@#$" and so on.

Answer 1

Python already has built-in support for encoding and decoding uuencoded messages.

from codecs import encode  # decode also works
print(encode("my message", 'uu'))
# -> 'begin 666 <data>\n*;7D@;65S<V%G90  \n \nend\n'

Internally python uses the binascii package to encode or decode the message line by line. We can use that to encode a single byte or even all bytes in the range(64) (because uuencoding tranforms 6bit into an ascii character: 2**6 == 64).

To generate all necessary bit patterns we can count to 64 and shift the result by 2 bit to the left. That way the highest 6 bits count from 0 to 64. Then it's just a matter of converting that into python bytes, uuencode them and extract the actual character.

In python2

from binascii import b2a_uu
for byte in range(64):
    pattern = chr(byte << 2)  # str and bytes are identical in python2
    encoded = b2a_uu(pattern)
    character = encoded[1]  # encoded[0] is the character count in that line
    print "{:2} -> {!r}".format(byte, character)

In python3 the first part is a little bit ugly.

from binascii import b2a_uu
for byte in range(64):
    pattern = bytes([byte << 2])  # chr().encode() will not work!
    encoded = b2a_uu(pattern)
    character = chr(encoded[1]) 
    print(f"{byte:2} -> {character!r}")

Thanks to Mark Ransom who explained why the bit shifting actually works.