Question

I’m writing this function that checks if a list of lists would be a valid sudoku puzzle. When I’m checking the lists for valid integers I’m getting unexpected results.

For example:

lst = [[1,2,3],[2,3,1],[4,2,1]]
for i in lst: 
  for v in i:
    print type(v)

<type 'int'>   #all the way through

for i in lst:
  for v in i:
    if v is int:
      print True

Prints nothing, and when I through in:

for i in lst:
  for v in i:
    if v is not int:
      print False

Prints all False? Not sure about what is going on, especially with the type showing they’re integers.

Answer 1

Instead of saying

if v is int:

Which is asking if v is the actual type int

Say

if isinstance(v, int):

which says v is an instantiated int (or subclass)

Here is an example, first with an integer (or instantiated int)

>>> v = 17
>>> type(v)
<type 'int'>
>>> v is int
False
>>> isinstance(v, int)
True
>>> 

Next with a type

>>> v = int
>>> type(v)
<type 'type'>
>>> v is int
True
>>> isinstance(v, int)
False
>>>