- Notifications
You must be signed in to change notification settings - Fork27
A fast, powerful, and extensible dice engine for D&D, d20 systems, and any other system that needs dice!
License
avrae/d20
Folders and files
| Name | Name | Last commit message | Last commit date | |
|---|---|---|---|---|
Repository files navigation
A fast, powerful, and extensible dice engine for D&D, d20 systems, and any other system that needs dice!
- Quick to start - just use
d20.roll()! - Optimized for speed and memory efficiency
- Highly extensible API for custom behaviour and dice stringification
- Built-in execution limits against malicious dice expressions
- Tree-based dice representation for easy traversal
Requires Python 3.6+.
python3 -m pip install -U d20
>>>importd20>>>result=d20.roll("1d20+5")>>>str(result)'1d20 (10) + 5 = `15`'>>>result.total15>>>result.crit<CritType.NORMAL:0>>>>str(result.ast)'1d20 + 5'
Check out the docs onRead the Docs!
This is the grammar supported by the dice parser, roughly ordered in how tightly the grammar binds.
These are the atoms used at the base of the syntax tree.
| Name | Syntax | Description | Examples |
|---|---|---|---|
| literal | INT,DECIMAL | A literal number. | 1,0.5,3.14 |
| dice | INT? "d" (INT | "%") | A set of die. | d20,3d6 |
| set | "(" (num ("," num)* ","?)? ")" | A set of expressions. | (),(2,),(1, 3+3, 1d20) |
Note that(3d6) is equivalent to3d6, but(3d6,) is the set containing the one element3d6.
These operations can be performed on dice and sets.
| Name | Syntax | Description | Examples |
|---|---|---|---|
| set_op | operation selector | An operation on a set (see below). | kh3,ro<3 |
| selector | seltype INT | A selection on a set (see below). | 3,h1,>2 |
Operators are always followed by a selector, and operate on the items in the set that match the selector.
| Syntax | Name | Description |
|---|---|---|
| k | keep | Keeps all matched values. |
| p | drop | Drops all matched values. |
| rr | reroll | Rerolls all matched values until none match. (Dice only) |
| ro | reroll once | Rerolls all matched values once. (Dice only) |
| ra | reroll and add | Rerolls up to one matched value once, keeping the original roll. (Dice only) |
| e | explode on | Rolls another die for each matched value. (Dice only) |
| mi | minimum | Sets the minimum value of each die. (Dice only) |
| ma | maximum | Sets the maximum value of each die. (Dice only) |
Selectors select from the remaining kept values in a set.
| Syntax | Name | Description |
|---|---|---|
| X | literal | All values in this set that are literally this value. |
| hX | highest X | The highest X values in the set. |
| lX | lowest X | The lowest X values in the set. |
| >X | greater than X | All values in this set greater than X. |
| <X | less than X | All values in this set less than X. |
| Syntax | Name | Description |
|---|---|---|
| +X | positive | Does nothing. |
| -X | negative | The negative value of X. |
| Syntax | Name |
|---|---|
| X * Y | multiplication |
| X / Y | division |
| X // Y | int division |
| X % Y | modulo |
| X + Y | addition |
| X - Y | subtraction |
| X == Y | equality |
| X >= Y | greater/equal |
| X <= Y | less/equal |
| X > Y | greater than |
| X < Y | less than |
| X != Y | inequality |
>>>fromd20importroll>>>r=roll("4d6kh3")# highest 3 of 4 6-sided dice>>>r.total14>>>str(r)'4d6kh3 (4, 4, **6**, ~~3~~) = `14`'>>>r=roll("2d6ro<3")# roll 2d6s, then reroll any 1s or 2s once>>>r.total9>>>str(r)'2d6ro<3 (**~~1~~**, 3, **6**) = `9`'>>>r=roll("8d6mi2")# roll 8d6s, with each die having a minimum roll of 2>>>r.total33>>>str(r)'8d6mi2 (1 -> 2, **6**, 4, 2, **6**, 2, 5, **6**) = `33`'>>>r=roll("(1d4 + 1, 3, 2d6kl1)kh1")# the highest of 1d4+1, 3, and the lower of 2 d6s>>>r.total3>>>str(r)'(1d4 (2) + 1, ~~3~~, ~~2d6kl1 (2, 5)~~)kh1 = `3`'
By default, d20 stringifies the result of each dice roll formatted in Markdown, which may not be useful in your application.To change this behaviour, you can create a subclass ofd20.Stringifier(ord20.SimpleStringifier as a starting point), and implement the_str_* methods to customize how your dice tree is stringified.
Then, simply pass an instance of your stringifier into theroll() function!
>>>importd20>>>classMyStringifier(d20.SimpleStringifier):...def_stringify(self,node):...ifnotnode.kept:...return'X'...returnsuper()._stringify(node)......def_str_expression(self,node):...returnf"The result of the roll{self._stringify(node.roll)} was{int(node.total)}">>>result=d20.roll("4d6e6kh3",stringifier=MyStringifier())>>>str(result)'The result of the roll 4d6e6kh3 (X, 5, 6!, 6!, X, X) was 17'
Each dice node supports value annotations - i.e., a method to "tag" parts of a roll with some indicator. For example,
>>>fromd20importroll>>>str(roll("3d6 [fire] + 1d4 [piercing]"))'3d6 (3, 2, 2) [fire] + 1d4 (3) [piercing] = `10`'>>>str(roll("-(1d8 + 3) [healing]"))'-(1d8 (7) + 3) [healing] = `-10`'>>>str(roll("(1 [one], 2 [two], 3 [three])"))'(1 [one], 2 [two], 3 [three]) = `6`'
are all examples of valid annotations. Annotations are purely visual and do not affect the evaluation of the roll by default.
Additionally, whenallow_comments=True is passed toroll(), the result of the roll may have a comment:
>>>fromd20importroll>>>result=roll("1d20 I rolled a d20",allow_comments=True)>>>str(result)'1d20 (13) = `13`'>>>result.comment'I rolled a d20'
Note that whileallow_comments is enabled, AST caching is disabled, which may lead to slightly worse performance.
The raw results of dice rolls are returned inExpressionobjects, which can be accessed as such:
>>>fromd20importroll>>>result=roll("3d6 + 1d4 + 3")>>>str(result)'3d6 (4, **6**, **6**) + 1d4 (**1**) + 3 = `20`'>>>result.expr<Expressionroll=<BinOpleft=<BinOpleft=<Dicenum=3size=6values=[<Diesize=6values=[<Literal4>]>,<Diesize=6values=[<Literal6>]>,<Diesize=6values=[<Literal6>]>]operations=[]>op=+right=<Dicenum=1size=4values=[<Diesize=4values=[<Literal1>]>]operations=[]>>op=+right=<Literal3>>comment=None>
or, in a easier-to-read format,
<Expression roll=<BinOp left=<BinOp left=<Dice num=3 size=6 values=[ <Die size=6 values=[<Literal 4>]>, <Die size=6 values=[<Literal 6>]>, <Die size=6 values=[<Literal 6>]> ] operations=[] > op=+ right=<Dice num=1 size=4 values=[ <Die size=4 values=[<Literal 1>]> ] operations=[] > > op=+ right=<Literal 3> > comment=None>From here,Expression.children returns a tree of nodes representing the expression from left to right, each of whichmay have children of their own. This can be used to easily search for specific dice, look for the left-most operand,or modify the result by adding in resistances or other modifications.
Finding the left and right-most operands:
>>>fromd20importroll>>>binop=roll("1 + 2 + 3 + 4")>>>left=binop.expr>>>whileleft.children:...left=left.children[0]>>>left<Literal1>>>>right=binop.expr>>>whileright.children:...right=right.children[-1]>>>right<Literal4>>>>fromd20importutils# these patterns are available in the utils submodule:>>>utils.leftmost(binop.expr)<Literal1>>>>utils.rightmost(binop.expr)<Literal4>
Searching for the d4:
>>>fromd20importroll,Dice,SimpleStringifier,utils>>>mixed=roll("-1d8 + 4 - (3, 1d4)kh1")>>>str(mixed)'-1d8 (**8**) + 4 - (3, ~~1d4 (3)~~)kh1 = `-7`'>>>root=mixed.expr>>>result=utils.dfs(root,lambdanode:isinstance(node,Dice)andnode.num==1andnode.size==4)>>>result<Dicenum=1size=4values=[<Diesize=4values=[<Literal3>]>]operations=[]>>>>SimpleStringifier().stringify(result)'1d4 (3)'
As a note, even though aDice object is the parent ofDie objects,Dice.children returns an empty list, since it'smore common to look for the dice, and not each individual component of that dice.
By default, the parser caches the 256 most frequently used dice expressions in an LFU cache, allowing for a significantspeedup when rolling many of the same kinds of rolls. This caching is disabled whenallow_comments is True.
With caching:
$ python3 -m timeit -s"from d20 import roll""roll('1d20')"10000 loops, best of 5: 21.6 usec per loop$ python3 -m timeit -s"from d20 import roll""roll('100d20')"500 loops, best of 5: 572 usec per loop$ python3 -m timeit -s"from d20 import roll; expr='1d20+'*50+'1d20'""roll(expr)"500 loops, best of 5: 732 usec per loop$ python3 -m timeit -s"from d20 import roll""roll('10d20rr<20')"1000 loops, best of 5: 1.13 msec per loop
Without caching:
$ python3 -m timeit -s"from d20 import roll""roll('1d20')"5000 loops, best of 5: 61.6 usec per loop$ python3 -m timeit -s"from d20 import roll""roll('100d20')"500 loops, best of 5: 620 usec per loop$ python3 -m timeit -s"from d20 import roll; expr='1d20+'*50+'1d20'""roll(expr)"500 loops, best of 5: 2.1 msec per loop$ python3 -m timeit -s"from d20 import roll""roll('10d20rr<20')"1000 loops, best of 5: 1.26 msec per loop
About
A fast, powerful, and extensible dice engine for D&D, d20 systems, and any other system that needs dice!