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Add formula for calculating SRM #10

Merged
merged 2 commits into from
Dec 27, 2018
Merged

Add formula for calculating SRM #10

merged 2 commits into from
Dec 27, 2018

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shouptech
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I have added a formula to the Recipe class which will calculate a recipe's color in units SRM.

hotzenklotz
hotzenklotz reviewed Dec 27, 2018
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pybeerxml/recipe.py Outdated Show resolved Hide resolved
hotzenklotz
hotzenklotz reviewed Dec 27, 2018
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Thank you very much for the contribution. Calculating the color is a great idea. Please check my code suggestion before merging.

Happy Holidays!

@hotzenklotz
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I just double-checked the brew wiki reference page. Apparently, in the provided formula the malt weight needs to be in pounds (lbs). The same is true for the batch size / amount of water. It needs to be in gallons.

According to the BeerXML specification all volume and weight units are metric. (liters and kilogram) http://www.beerxml.com/beerxml.htm

Therefore, the color implementation is wrong as is. I suppose it can easily be fixed by converting the units accordingly.
@shouptech Have you checked the color values from the example recipes used in the unit tests with another program?

@shouptech
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The formula is correct. 8.3453 is the conversion factor from kg/L to lb/gal. I checked it against BeerSmith and it's within a hundredth of SRM.

@shouptech
Multiple fixes for color calculation
82f5b49 
* `mcu` default value is now a float
* Check for fermentable amount and color for `None`
* Correct metric to imperial conversion factor
* Add test to ensure color updates for recipe are ignored
@shouptech
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I've updated this PR with a new commit. Please review.

Thanks!

hotzenklotz
hotzenklotz approved these changes Dec 27, 2018
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pybeerxml/recipe.py
mcu = 0.0
for f in self.fermentables:
if f.amount is not None and f.color is not None:
# 8.3454 is conversion factor from kg/L to lb/gal
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👍

@hotzenklotz hotzenklotz merged commit 7102b7c into hotzenklotz:master Dec 27, 2018
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@shouptech I released version 1.0.6 on PyPi which includes your PR. Thank you very much.

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@hotzenklotz hotzenklotz hotzenklotz approved these changes

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@shouptech @hotzenklotz