debug.py - 03:42:15 def find_bug(): for i in range(len(data)): if data[i] == None: # <-- here? print(f"found it: {i}") return i return -1 >>> find_bug() Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 2, in find_bug TypeError: object of type 'NoneType' has no len() >>> data = None # oh. 3:42 AM