One possibility to get what you want is to use Python string formatting.

This can be done the old way with `%`

and the new way with `{}`

and `.format`

.
The old way will accept many types of numbers, the new way requires
the entry to have the type of a Python float.

Here is an illustration of both, with 72 digits after the decimal point.

```
sage: a = 1/2^70
sage: '%.72f' % a
'0.000000000000000000000847032947254300339068322500679641962051391601562500'
sage: '{:.72f}'.format(float(a))
'0.000000000000000000000847032947254300339068322500679641962051391601562500'
```

Combine with `print`

to get those displayed without the surrounding `'`

quotes.

```
sage: a = 1/2^70
sage: aa = '%.72f' % a
sage: print(aa)
0.000000000000000000000847032947254300339068322500679641962051391601562500
sage: ab = '{:.72f}'.format(float(a))
sage: print(ab)
0.000000000000000000000847032947254300339068322500679641962051391601562500
```

Related reading: