[Python-Dev] PEP 8: Discourage named lambdas? (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Sun May 4 08:13:08 CEST 2008

I guess that's inevitable (given lambda's existence... and human nature;-) and about on the same plane as another hatefully redundant construct I find myself having to beat upon over and over in code reviews:

if : result = True else: result = False return result vs the simple "return " [[or bool() if it's actually mandatory to return a bool and can't be relied upon to produce one]].

Indeed, I think these are the same phenomenons. If lambdas where not available, people would, instead of writing

Thread(target = lambda: foo())

write

def target(): foo() Thread(target = target)

Your example above demonstrates that the boolean type is a concept that is very difficult to grasp (not the notion of boolean expressions, which are easy to understand - it's the boolean type that is difficult, i.e. that a boolean expression can be used not just in conditional statements, but also assigned to variables, returned, etc.).

When I ask students in the exam to rewrite your code above (and assuming they use Java), so that "it is a single line", they typically write

return ? true : false;

Likewise, apparently, the notion of generic callables is difficult to understand. Unless you have written it yourself, you won't recognize an expression as callable.

Regards, Martin

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