callableExpressionParser 1.0.2

Math Expression Parser that works with [ + - * / ^ // ! ] operators, constants [ pi ], functions [ exp, log, ln ], strings ["testString"], and [variables] out of the box and can be expanded to cover more use cases!

mathExpressionParser

Math Expression Parser that works with [ + - * / ^ // ! ] operators, constants [ pi ], functions [ exp, log, ln ], strings ["testString"], and [variables] out of the box and can be expanded to cover more use cases!

Motivation

A lot of the math expression parsers I found online didn't quite cover all the use cases I needed as well as were hard to expand upon. With that, I created my own!

How To Install

pip install callableExpressionParser

How To Use

Regardless of the language, you'll primarily use 2 lines of code in order.

1. createExpressionTree - This function takes the list of nodes from extractNodes or an expression string and parses its nodes and creates a binary tree. Each parent node is an operator or a function, and each child node is a number, constant, or token group. This function returns the base node of the tree which you can call exec() on to prepare the tree.
2. The result of the base Node's exec() function is a function that takes in an optional dictionary argument. If any variables are defined in the expression, the variables will be replaced with the dictionary key-value where the key is the variable's name.

What's great about this approach is say you have a table represented as a list of dictionaries. If you'd want to add a calculated column that is some expression based on other row values, you can create the new column easily.

Example in python

from callableExpressionParser import createExpressionTree

tbl = [{'a': 1, 'b': 2},{'a': 3, 'b': 4},{'a': 5, 'b': 6}]
expression = '[a]+2*[b]'
func = createExpressionTree(expression=expression).exec()
tbl = [{**r, 'c': func(**r)} for r in tbl]
print(tbl) # [{'a': 1, 'b': 2, 'c': 5.0},{'a': 3, 'b': 4, 'c': 11.0},{'a': 5, 'b': 6, 'c': 17.0}]

Print the Binary Tree Expression

After an expression tree is created using createExpressionTree() you can call the display() function on the root node of the tree to see the Binary Tree printed out.
Shoutout to this Stack Overflow Answer for the code!

from callableExpressionParser import createExpressionTree
expression = '[a]+2*[b]'
root = createExpressionTree(expression=expression)
root.display()
#  +_
# /  \
# a  *
#   / \
#   2 b