I have a tuple:
details = ({}, []) As there is no data in the following tuple I want to return a null response. For this I am writing:
if not details: return Response({}) else: print "Not null" But this does not seem to work as it is always going in the else part and printing not null. I am new to python. Any help is appreciated.
Note: if you write:
if <expr>: passthen Python will not check that
<expr> == True, it will evaluate the truthiness of the<expr>. Objects have some sort of defined "truthiness" value. The truthiness ofTrueandFalseare respectivelyTrueandFalse. ForNone, the truthiness isFalse, for numbers usually the truthiness isTrueif and only if the number is different from zero, for collections (tuples, sets, dictionaries, lists, etc.), the truthiness isTrueif the collection contains at least one element. By default custom classes have alwaysTrueas truthiness, but by overriding the__bool__(or__len__), one can define custom rules.
The truthiness of tuple is True given the tuple itself contains one or more items (and False otherwise). What these elements are, is irrelevant.
In case you want to check that at least one of the items of the tuple has truthiness True, we can use any(..):
if not any(details): # all items are empty return Response({}) else: print "Not null"So from the moment the list contains at least one element, or the dictonary, or both, the else case will fire, otherwise the if body will fire.
If we want to check that all elements in the tuple have truthiness True, we can use all(..):
if not all(details): # one or more items are empty return Response({}) else: print "Not null"
details == True returns False, but if details: print('True') prints True in the prompt?if <expr> does not check that <expr> == True, ut evaluates the truthiness.
The accepted answer implies that any does not perform a deep search for truth. This is demonstrated below:
not not [] # False (double negation as truthness detector). not not ([],) # True not not any(([],)) # False not not any(([1],)) # True not not any(([None],)) # Still True, as expected. 
if not any(details):