Re: error in syntax description for comprehensions?
On 3/30/2017 4:57 PM, Boylan, Ross wrote: https://docs.python.org/3/reference/expressions.html#displays-for-lists-sets-and-dictionaries describes the syntax for comprehensions as comprehension ::= expression comp_for comp_for ::= [ASYNC] "for" target_list "in" or_test [comp_iter] comp_iter ::= comp_for | comp_if comp_if ::= "if" expression_nocond [comp_iter] Is the comp_for missing an argument after "in"? The or_test *is* the 'argument'. One has to follow the definition of or_test and its components, > but I can't find anything that results to a single variable > or expression. An or_test *is* a single expression. Like all python expressions, it evaluates to a python object. In this case, the object is passed to iter() and so the object must be an iterable. >>> a, b = None, range(3) >>> a or b range(0, 3) >>> for i in a or b: print(i) 0 1 2 -- Terry Jan Reedy -- https://mail.python.org/mailman/listinfo/python-list
Re: error in syntax description for comprehensions?
On Thursday, March 30, 2017 at 4:59:03 PM UTC-4, Boylan, Ross wrote: > https://docs.python.org/3/reference/expressions.html#displays-for-lists-sets-and-dictionaries > describes the syntax for comprehensions as > comprehension ::= expression comp_for > comp_for ::= [ASYNC] "for" target_list "in" or_test [comp_iter] > comp_iter ::= comp_for | comp_if > comp_if ::= "if" expression_nocond [comp_iter] > > Is the comp_for missing an argument after "in"? > One has to follow the definition of or_test and its components, but I can't > find anything that results to a single variable or expression. > > Actually, I'm not sure what or_test would do there either with or without an > additional element following "in". Syntax grammars can be obtuse. An or_test can be an and_test, which can be a not_test, which can be a comparison. It continues from there. The whole chain of "can be" is: or_test and_test not_test comparison or_expr xor_expr and_expr shift_expr a_expr m_expr u_expr power primary atom identifier ... and identifier is what you are looking for. --Ned. -- https://mail.python.org/mailman/listinfo/python-list
error in syntax description for comprehensions?
https://docs.python.org/3/reference/expressions.html#displays-for-lists-sets-and-dictionaries describes the syntax for comprehensions as comprehension ::= expression comp_for comp_for ::= [ASYNC] "for" target_list "in" or_test [comp_iter] comp_iter ::= comp_for | comp_if comp_if ::= "if" expression_nocond [comp_iter] Is the comp_for missing an argument after "in"? One has to follow the definition of or_test and its components, but I can't find anything that results to a single variable or expression. Actually, I'm not sure what or_test would do there either with or without an additional element following "in". Ross Boylan -- https://mail.python.org/mailman/listinfo/python-list
