I am new to python. I have a few questions coming from an armature!

[Chris Angelico]

On Fri, Aug 19, 2016 at 3:00 AM, Terry Reedy <tjreedy at udel.edu> wrote:
> On 8/18/2016 5:32 AM, Steven D'Aprano wrote:
>
>>> Beginners often do not understand that the body of a lambda expression
>>> is evaluated in a new local namespace, and only when the resulting
>>> function is called, the same as with a def statement.  They then neglect
>>> to capture current values when writing lambda expressions in a for loop.
>>
>>
>> Sure. But since the behaviour of def functions and lambda functions are
>> identical, writing a named def won't solve that problem.
>
>
> It will if people do not make the same mental mistake when writing a def,
> because they think def functions and 'lambdas' behave differently.
>
> I can't remember every seeing "my def function in a loop does not work
> right" while "my lambda in a loop does not work right" is distressingly
> common.  What I don't know is whether the sparsity of the former type of
> report is because those subject to the error get it right when they use def
> in a loop or because they never use def in a loop.

The latter. People who are confused about lambda in a loop are not
magically unconfused by def in a loop; in fact, I'd expect to see
*more* confusion, because those same people are likely to be confused
by the fact that a "declaration" can be done more than once and have
different effects. That is to say, a lambda function looks like it's
being created at the point where you use it, but a def function looks
like a declaration, which is independent of loops and stuff. I don't
have actual stats on how many people are confused by each, but I know
both points do cause confusion. Having def statements inside loops is
definitely [1] rarer than using lambda expressions inside loops.

ChrisA

[1] Pun intended. And I'm not sorry.