plusminus

The plusminus package provides a ready-to-run arithmetic parser and evaluator, based on pyparsing's infixNotation helper method.

Strings containing 6-function arithmetic expressions can be parsed and evaluated using the BasicArithmeticParser:

from plusminus import BasicArithmeticParser

parser = BasicArithmeticParser()
print(parser.evaluate("2+3/10"))

The parser can also return an Abstract Syntax Tree of ArithNode objects:

parsed_elements = parser.parse("2+3/10")

Arithmetic expressions are evaluated following standard rules for operator precedence, allowing for use of parentheses to override:

()
∩ & (set intersection)
∪ | (set union)
-
**
* / // × ÷ mod
+ -
< > <= >= == != ≠ ≤ ≥
in ∈ ∉
not
and ∧
or ∨
? : (ternary)

Functions can be called:

  sgn    min  asin  rad    gcd
  abs    max  acos  deg    lcm
  round  str  atan  ln     gamma
  trunc  sin  sinh  log    hypot
  ceil   cos  cosh  log2   rnd
  floor  tan  tanh  log10

The Basic ArithmeticParser also supports assignment of variables:

r = 5
area = π × r²

This last expression could be assigned using @= formula assignment:

area @= π × r²

As r is updated, evaluating area will be reevaluated using the new value.

Custom expressions can be defined using a simple API. Example parsers are included for dice rolling, combination/permutation expressions, and common business calculations. These parsers can be incorporated into other applications to support the safe evaluation of user-defined domain-specific expressions.