raymondhによるPython tips

Raymond Hettinger @raymondh

The persistent dictionary recipe has been updated to support context managers and to run in Py3.x: http://t.co/ygwIee6H

Raymond Hettinger @raymondh

#python tip: frozensets are hashable so you can use them as dict keys or as members of another set. This is handy for graph algorithms.

Raymond Hettinger @raymondh

#python3 note: 1 and None cannot be compared in Python 3, so lists with missing values need to be filtered before sorting.

Raymond Hettinger @raymondh

What can a #python list do that a tuple can't? set(dir(list)) - set(dir(tuple))

Raymond Hettinger @raymondh

#python proves euler wrong ;-) math.e ** (1j * math.pi) + 1 != 0

Raymond Hettinger @raymondh

#python tip: subprocess.check_output() is easy to learn, easy to use, and more than a little empowering.

Raymond Hettinger @raymondh

#python tip: Testing the result of str.find() seems to be a never ending source of bugs. Use with care or use str.index() instead.

Raymond Hettinger @raymondh

#python tip from Larry Hastings: shlex.split() works great with subprocess.Popen() and subprocess.check_output()

Raymond Hettinger @raymondh

#python tip: Rather than making multiple pickle.dumps to a single file, just combine the data into one list: dump([a,b], f)

Raymond Hettinger @raymondh

#python tip: For scripts that don't need "import site", python can be launched with the -S option to improve start-up time.

Raymond Hettinger @raymondh

#python tip: It is vital to use parentheses when catching multiple exceptions. "except IndexError, KeyError:" is a grievous error.

Raymond Hettinger @raymondh

else-clauses in #python's for/while loops are trivially easy to explain but some minds just rebel at the thought: http://t.co/HUhn1GrG

Raymond Hettinger @raymondh

Simple #python idiom for splitting sequences into chunks: [s[i: i+4096] for i in xrange(0, len(s), 4096)]

Raymond Hettinger @raymondh

Beginner #python? print '68656c6c6f20776f726c64'.decode('hex')

Raymond Hettinger @raymondh

#python tip: A handy and commonly over-looked builtin function is vars(). Works on classes, instances, modules, argparse namespaces, ...

Raymond Hettinger @raymondh

@alex_gaynor Instances with __slots__ don't have a dictionary so there's nothing for vars() to get.

Raymond Hettinger @raymondh

#python tip: Linux/Mac users should open binary files in the "rb" mode. That will avoid unpleasantness on Windows and on Py3.x

Raymond Hettinger @raymondh

The new HTTP response codes are great. http://t.co/DLixJ28d My favorite: 429 Too Many Requests

Raymond Hettinger @raymondh

Weak ordered set in #Python http://t.co/o6Ahp0CY

Raymond Hettinger @raymondh

#python tip: Learn to use double underscore name mangling for private intraclass calls: http://t.co/9r5qrFWG

Raymond Hettinger @raymondh

#python one-liner of the day: http://t.co/U0aLnOI1

Raymond Hettinger @raymondh

I was curious how often people use #python's open() in a for-loop, relying on implicit closing: http://t.co/YVvdj3vT

Raymond Hettinger @raymondh

#python library of the day: http://t.co/1Jlvuxii Easy to use symbolic equation solver in pure python (with extensive tests and comments).

Raymond Hettinger @raymondh

#python teaching anti-pattern: Student: how does this work? Teacher: it works like this. Heckler: but that doesn't work in Py3.x ...

Raymond Hettinger @raymondh

#python tip: If you don't want sqlite3 to return unicode strings, set conn.text_factory=str