Python is not very suitable for shell one-liners. You could play with The Pyed Piper:
$ ls | pyp "p[0] | pp.sort() | p + ' first letter, sorted!'"
# it gives sorted list of first letters of every line
It uses standard Python string and list methods as well as custom functions. There is also pyline:
$ ls | pyline -m os 'line and os.path.abspath(line.strip())'
$ ls | pyline -r '\(.*\)' 'rgx and (rgx.group(0), rgx.group(1)) or line'
$ ls | pyline -p 'p and p.abspath() or ("# ".format(line))'
Another alternative is to use ipython as a shell or a browser-based notebook (recommended). Or if you want more BASHwards-looking syntax and tab completion for subprocess commands; try xonsh as your shell:
xonsh$ [i*i for i in range(10)]
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
xonsh$ date -u
Tue Oct 6 04:25:27 UTC 2015
subprocess and its alternatives (plumbum, pexpect, sarge, sh (module), fabric) allow you to create arbitrary complex commands by exploiting the best of python and bash.
There are also several nice python -m one-liners e.g.:
$ python3 -m http.server # serve current directory over http
$ python -m zipfile # work with zipfiles
$ python -m calendar # show calendar
$ python -m telnetlib towel.blinkenlights.nl # Star Wars