in reply to Re^4: Evolution of python
in thread Evolution of python

Lexical variables and closures don't need each other, unless you define a closure as something that closes over its lexical variables.

x = "Hello"; # a global variable
def make_closure(arg):
    arg = arg # make arg a lexical variable
    return lambda y, arg=arg: print(x,y,arg)

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The indentation or braces are (mostly) equivalent in defining where a name/value binding may be visible, but that has nothing to do with closures.

And the OP issue of not knowing where/how a variable can be declared limited to a scope isn't an issue IMO because both Perl and Python have variables with limited scope which aren't visible "upwards".

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Re^6:Evolution of python
by LanX (Saint) on Jul 07, 2019 at 19:52 UTC
    > Lexical variables and closures don't need each other,

    a "closure" over a global variable is commonly known as a function using a global variable ...

    IMHO that's far too trivial to be called a closure. :-p

    Not sure why you are doing this

        arg = arg # make arg a lexical variable

    arg should be a lexical var right away.

    you might want to compare this, a is a lexical and clos a generated closure

    >>> def test(a):
...   def clos():
...     return a
...   return clos
... 
>>> x=test(1)
>>> y=test(22)
>>> x()
1
>>> y()
22

    [download]

    This is pretty much a demonstration of lexical scope, you will only deal with dynamic scope when using global vars or accessing class attributes.*

    Update

    *) Well if functions call each other and close over the same lexical one might call this a dynamic scope too.

    For instance a recursive closure.

    Cheers Rolf
    (addicted to the Perl Programming Language :)
    Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

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