Remove pointless discussion of the lack of a ternary operator
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@ -769,52 +769,6 @@ Yes, this feature was added in Python 2.5. The syntax would be as follows::
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For versions previous to 2.5 the answer would be 'No'.
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.. XXX remove rest?
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In many cases you can mimic ``a ? b : c`` with ``a and b or c``, but there's a
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flaw: if *b* is zero (or empty, or ``None`` -- anything that tests false) then
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*c* will be selected instead. In many cases you can prove by looking at the
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code that this can't happen (e.g. because *b* is a constant or has a type that
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can never be false), but in general this can be a problem.
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Tim Peters (who wishes it was Steve Majewski) suggested the following solution:
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``(a and [b] or [c])[0]``. Because ``[b]`` is a singleton list it is never
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false, so the wrong path is never taken; then applying ``[0]`` to the whole
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thing gets the *b* or *c* that you really wanted. Ugly, but it gets you there
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in the rare cases where it is really inconvenient to rewrite your code using
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'if'.
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The best course is usually to write a simple ``if...else`` statement. Another
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solution is to implement the ``?:`` operator as a function::
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def q(cond, on_true, on_false):
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if cond:
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if not isfunction(on_true):
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return on_true
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else:
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return on_true()
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else:
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if not isfunction(on_false):
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return on_false
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else:
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return on_false()
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In most cases you'll pass b and c directly: ``q(a, b, c)``. To avoid evaluating
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b or c when they shouldn't be, encapsulate them within a lambda function, e.g.:
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``q(a, lambda: b, lambda: c)``.
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It has been asked *why* Python has no if-then-else expression. There are
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several answers: many languages do just fine without one; it can easily lead to
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less readable code; no sufficiently "Pythonic" syntax has been discovered; a
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search of the standard library found remarkably few places where using an
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if-then-else expression would make the code more understandable.
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In 2002, :pep:`308` was written proposing several possible syntaxes and the
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community was asked to vote on the issue. The vote was inconclusive. Most
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people liked one of the syntaxes, but also hated other syntaxes; many votes
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implied that people preferred no ternary operator rather than having a syntax
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they hated.
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Is it possible to write obfuscated one-liners in Python?
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--------------------------------------------------------
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