#### Overview of this book

Python for Finance
Credits
Acknowledgments
www.PacktPub.com
Preface
Free Chapter
Introduction and Installation of Python
13 Lines of Python to Price a Call Option
Introduction to Modules
Statistical Analysis of Time Series
Index

## Choosing appropriate precision

The default precision for Python has 16 decimal places as shown in the following example. This is good enough for most finance-related problems or research:

```>>>7/3
2.3333333333333335
```

We could use the `round()` function to change the precision as follows:

```>>>payment1=3/7
>>>payment1
0.42857142857142855
>>>payment2=round(y,5)
>>>payment2
0.42857
```

Assume that the units for both `payment1` and `payment2` are in millions. The difference could be huge after we apply the `round()` function with just two decimal places! If we use one dollar as our unit, the exact payment is \$428,571. However, if we use millions instead and apply two decimal places, we end up with 430,000, which is shown in the following example. The difference is \$1,429:

```>>>payment1*10**6
428571.4285714285
>>>payment2=round(payment1,2)
>>>payment2
0.43
>>>payment2*10**6
430000.0
```