16 Apr 2007 avassalotti   » (Journeyer)

Boosted Python Startup

Yesterday, I was reading Peter Norvig’s excellent article about spell checking. Then, I started to look to some of his older stuff. So, I found his Python IAQ (Infrequently Answered Questions), and discovered a pretty neat trick:

h = [None]  # history

class Prompt:
    """A prompt a history mechanism.
    From http://www.norvig.com/python-iaq.html
    def __init__(self, prompt='h[%d] >>> '):
        self.prompt = prompt

    def __str__(self):
            if _ not in h: h.append(_)
        except NameError:
        return self.prompt % len(h)

    def __radd__(self, other):
        return str(other) + str(self)

sys.ps1 = Prompt()
sys.ps2 = '     ... '

This improve the interactive prompt of Python with a shell-like history mechanism. With this prompt, you can reuse any previous value returned by Python. For example:

h[1] >>> lambda x: x * 2
<function <lambda> at 0xb7dab41c>
h[2] >>> [1, 2, 3, 4, 5]
[1, 2, 3, 4, 5]
h[3] >>> map(h[1], h[2])
[2, 4, 6, 8, 10]

You can make it your default prompt, by adding the above in your .pythonrc.py. You will need to specify its location to Python with the environment variable PYTHONSTARTUP. Just add something like the following to your shell configuration (e.g., .bashrc or .zshrc).

export PTHONSTARTUP="$HOME/.pythonrc.py"

I am sure there is a ton of other useful modifications, which can be done with the startup file of Python. If you’re interested, here my brand new startup file. And if you know any other cool tricks for Python, please tell me!

Syndicated 2007-04-16 02:36:05 (Updated 2007-05-07 19:28:34) from Alexandre Vassalotti

Latest blog entries     Older blog entries

New Advogato Features

New HTML Parser: The long-awaited libxml2 based HTML parser code is live. It needs further work but already handles most markup better than the original parser.

Keep up with the latest Advogato features by reading the Advogato status blog.

If you're a C programmer with some spare time, take a look at the mod_virgule project page and help us with one of the tasks on the ToDo list!