1 | initial version |

To convert a string to an expression in Sage's symbolic ring, use `SR(expression)'.

Here is how it would work with your example.

```
sage: x1, x2, x3 = SR.var('x1 x2 x3')
sage: expression = "x1^2*x2*x3*4"
sage: ex = SR(expression)
sage: ex
4*x1^2*x2*x3
```

2 | No.2 Revision |

To convert a string `expression`

to ~~an ~~any parent `X`

in Sage, you could do `X(expression)`

.

Thus, to convert the expression ~~in ~~to Sage's symbolic ring, use ~~`SR(expression)'.~~`SR(expression)`

.

Here is how it would work with your example.

```
sage: x1, x2, x3 = SR.var('x1 x2 x3')
sage: expression = "x1^2*x2*x3*4"
sage: ex = SR(expression)
sage: ex
4*x1^2*x2*x3
```

If you prefer to work with a polynomial ring:

```
sage: P.<x1, x2, x3> = QQ[]
sage: f = P(expression)
sage: f
4*x1^2*x2*x3
```

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