A strange value in dictionary

[python_user_n]

Hello,
I'm trying to write a solution for exercise 12.4 from "Think Python", and I have a strange behavior of my return value.
Here's the code:

def tuple_list_dict_init(w_list):
	"""
	Return a dictionary that have as keys tuples of letters(sorted) from words in a given list.
	w_list:	a given list of words. Should be of type list of strings.
	d = dict()
	"""
	for l in w_list:					#	this loop for test purposes only
		if (type(l) is int):
			print('Integer detected')
	
	for w in w_list:
		if (type(tuple(sorted(w))) is int):		#	this conditional for test purposes only
			print('Integer key detected')
		d.setdefault(tuple(sorted(w)), [])
		
	return d

When I call this function no 'print' is executed. But in the returned dictionary I can find key of type 'int'.
Where is the error? Thank you.