And since `c1` and `c2` are not integers, but Polys, this definitely won't work. `is` is **exact** comparison in Python. It only returns True if the two items are exactly the same in memory. It is almost never what you want. `==` compares if two things are equal in a more mathematical sense. For example

```py
>>> a = []
>>> b = []
>>> a is b
False
>>> a == b
True
```