1 | initial version |

You defined

```
sage: a = sum(sqrt(x), x, 0, oo); a
sum(sqrt(x), x, 0, +Infinity)
```

Let us explore this object.

```
sage: a.parent()
Symbolic Ring
```

Typing `a.`

and pressing the tab key, we find among other
methods the following two.

```
sage: a.operator()
sum
sage: a.operands()
[sqrt(x), x, 0, +Infinity]
```

So we can define a function that will replace `+Infinity`

by `n`

:

```
sage: def partial(a,n):
....: return a.operator()(*(a.operands()[:-1]+[n]))
....:
sage: partial(a,10)
sum(sqrt(x), x, 0, 10)
```

and use it to get the first few partial sums:

```
sage: for n in xrange(5r):
....: print partial(a,n)
....:
sum(sqrt(x), x, 0, 0)
sum(sqrt(x), x, 0, 1)
sum(sqrt(x), x, 0, 2)
sum(sqrt(x), x, 0, 3)
sum(sqrt(x), x, 0, 4)
```

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