Exponential of very small number in python

Question

I am trying to calculate the exponential of -1200 in python (it's an example, I don't need -1200 in particular but a collection of numbers that are around -1200). ``` >>> math.exp(-1200) 0.0 ``` It is giving me an underflow; How may I go around this problem? Thanks for any help :)

Accepted Answer

In the standard library, you can look at the `decimal` module:

```
>>> import decimal
>>> decimal.Decimal(-1200)
Decimal('-1200')
>>> decimal.Decimal(-1200).exp()
Decimal('7.024601888177132554529322758E-522')
```

If you need more functions than `decimal` supports, you could look at the library `mpmath`, which I use and like a lot:

```
>>> import mpmath
>>> mpmath.exp(-1200)
mpf('7.0246018881771323e-522')
>>> mpmath.mp.dps = 200
>>> mpmath.exp(-1200)
mpf('7.0246018881771325545293227583680003334372949620241053728126200964731446389957280922886658181655138626308272350874157946618434229308939128146439669946631241632494494046687627223476088395986988628688095132e-522')
```

but if possible, you should see if you can recast your equations to work entirely in the log space.

Exponential of very small number in python

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