# How to get sage to keep the same form as an expression from sympy?

I have this expression:

$$-\frac{2}{3} t_{1} + \frac{2}{3} y_{1}$$

and would like to rewrite it as follows:

$$\frac{2}{3} (-t_1 + y_1)$$

Using sympy, I can get something close:

```
import sympy as sp
var('y1 t1')
expr1 = -2/3*t1 + 2/3*y1
sp.factor(sp.sympify(expr1))
```

This gives:

```
๐ธ*(โฏ๐๐ท+๐ข๐ท)/๐น
```

But when I convert it back to Sage:

```
sp.factor(sp.sympify(expr1))._sage_()
```

The result reverts to `expr1`

.

How can I get the call to `_sage_()`

not do any rewrites on the sympy expression?

Is the following (purely) algebraic framework ok?