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| -rw-r--r-- | bot/resources/tags/floats.md | 19 |
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diff --git a/bot/resources/tags/floats.md b/bot/resources/tags/floats.md new file mode 100644 index 000000000..4b0651930 --- /dev/null +++ b/bot/resources/tags/floats.md @@ -0,0 +1,19 @@ +**Floating Point Arithmetic** +You may have noticed that when doing arithmetic with floats in Python you sometimes get strange results, like this: +```python +>>> 0.1 + 0.2 +0.30000000000000004 +``` +**Why this happens** +Internally your computer stores floats as as binary fractions. Many decimal values cannot be stored as exact binary fractions, which means an approximation has to be used. + +**How you can avoid this** +If you require an exact decimal representation, you can use the [decimal](https://docs.python.org/3/library/decimal.html) or [fractions](https://docs.python.org/3/library/fractions.html) module. Here is an example using the decimal module: +```python +>>> from decimal import Decimal +>>> Decimal('0.1') + Decimal('0.2') +Decimal('0.3') +``` +Note that we enter in the number we want as a string so we don't pass on the imprecision from the float. + +For more details on why this happens check out this [page in the python docs](https://docs.python.org/3/tutorial/floatingpoint.html) or this [Computerphile video](https://www.youtube.com/watch/PZRI1IfStY0). |