[Tutor] Use of "or" in a lambda expression

[boB Stepp]

On Sat, Apr 4, 2015 at 12:34 PM, Steven D'Aprano <steve at pearwood.info> wrote:
> On Sat, Apr 04, 2015 at 11:49:08AM -0500, boB Stepp wrote:
>> Windows 7, Python 3.4.3
>>
>> This code snippet is "Example 7-13" on page 383 from "Programming
>> Python, 4th ed." by Mark Lutz :
>>
>> import sys
>> from tkinter import *
>>
>> widget = Button(None,
>>             text='Hello event world!',
>>             command=(lambda: print('Hello lambda world!') or sys.exit()))
>
> o_O
>
> That's either the most horrible misuse of lambda I've ever seen, or a
> really cool and rather nifty trick. I'm not sure which :-)

Re-reading the paragraph relevant to Mr. Lutz's example, perhaps I
should quote the full paragraph:

"This code is a bit tricky because lambdas can contain only an
expression; to emulate the original script, this version uses an or
operator to force two expressions to be run (print works as the first,
because it's a function call in Python 3.X--we don't need to resort to
using sys.stdout directly)."

I think the key thought of the author here is he showing how to
rewrite an earlier example that explicitly defines a quit() function,
which both prints and then exits the program,  to using a lambda
expression. I don't think his intent is to say that the lambda
expression is to be preferred (Or is he?).

To my mind, would:

def quit():
    print('Hello lambda world!')
    sys.exit()

and:

widget = Button(None, text='Hello event world!', command=quit)

be preferable Python style?

boB