Python: misc one-liners and snippets

Formatted date to datetime object

import time, datetime
timestring = "2005-09-01 12:30:09"
time_format = "%Y-%m-%d %H:%M:%S"
datetime.datetime.strptime(timestring, time_format)

Punycode URLs

domain = '\xd8\xa7\xd9\x84\xd8\xa7\xd8\xb9\xd9\x84\xd9\x8a-\xd9\x84\xd9'\
    '\x84\xd8\xa7\xd8\xaa\xd8\xb5\xd8\xa7\xd9\x84\xd8\xa7\xd8\xaa.\xd9'\
    '\x82\xd8\xb7\xd8\xb1'
domain_unicode = unicode(domain, "utf8")
domain_idna = domain_unicode.encode("idna")

or

domain = u'\u0627\u0644\u0627\u0639\u0644\u064a-\u0644\u0644\u0627\u062a'\
    '\u0635\u0627\u0644\u0627\u062a.\u0642\u0637\u0631'
domain_idna = domain.encode("idna")

Save Python shell history

To save all the commands history of the current Python shell, use the readline module as follows:

import readline
readline.write_history_file('/tmp/my-history-file')

Lazy property

Like @property, but lazy (the returned value will be cached in the object).

def lazy_property(fn):
    attr_name = '_lazy_' + fn.__name__

    def getter(self):
        if not hasattr(self, attr_name):
            setattr(self, attr_name, fn(self))
        return getattr(self, attr_name)

    def setter(self, value):
        setattr(self, attr_name, value)

    def deleter(self):
        delattr(self, attr_name)

    return property(fget=getter, fset=setter, fdel=deleter, doc=fn.__doc__)

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