Question

consider this simple function

def foo(l=[]):
    if not l:  print "List is empty"
    else : print "List is not empty"

Now let’s call foo

x=[]
foo(x)
#List is empty

foo('')
#List is empty

But if x=[”] the list is not considered as empty!!!

x=['']
foo(x)
#List is not empty

Questions –

1. Why list of empty values are not considered as empty? (In case of variable it is considered as empty e.g.)

   x=''
   if x:print 'not empty!!'
   else: print 'empty'
   

2. How can I modify function foo() so that list will be considered as empty in all these cases: x=[] , x=[''], x=['', '']

Answer 1

Using the built-in any()

def foo(l=[]):
    if any(l):
        print 'List is not empty'
    else:
        print 'List is empty'

foo([''])
# List is empty