Hello, I recently realized the following, and wonder whether there is a reason for this, which I am unable to figure out. A list comp can both map and filter: [x*x for x in numbers if x%2==1] When it only maps, we can simply get rid of the filter part: [x*x for x in numbers] Meaning we are not forced to write: [x*x for x in numbers if True] But the analog does not apply to filter-only list comps: [x in numbers if x%2==1] # SyntaxError Why? I find this syntax clear, actually clearer than [x for x in numbers if x%2==1] that confusingly repeats the item. Would there be any parsing issue if we let down "<expression> for" when it does nothing? Side note: I find the core part of a comprehension be "<item> in <collection>": [item in collection] would be equivalent to list(collection). (item in collection) would just build an iterator on collection. From this POV, this core can be preceded by a mapping expression and/or followed by a filtering condition. Denis -- ________________________________ la vita e estrany spir.wikidot.com