### Coefficients of a constant polynomial

If have a list A of polynomials in x and y and
want the coefficients of x. Here is what I do:

```
var('y')
```

` `A = [x, y, x*y + 3*y^2]

```
for p in A :
print p.coefficients(x)
```

And here is what I get:

```
[[1, 1]]
```

` `[[y, 0]]

```
[[3*y^2, 0], [y, 1]]
```

That's fine. My next list to process is

```
B = [1, x, y, x
```*y + 3*y^2]

And here is what I get:

AttributeError: 'sage.rings.integer.Integer' object has no attribute 'coefficients'.

I expected the answer 0 as the coefficient of x of the polynomial p(x, y) = 1 is 0.

How do I get around this behavior of Sage?