exenifix/strmath

A module for evaluating math expressions without eval()

strmath

A module for evaluating math expressions without eval(). Currently the module supports only simple math operations (eg. multiplication, subtraction, division, %) but in the future there will be functions support.

Installation

The module is available for installation from PyPI

$ pip install strmath

Basic Usage

from strmath import evaluate


result = evaluate("(90 + 2) // 4")
print(result)

Accuracy

As tests show, the library is 100% accurate with python native evaluation:

+----------------+--------+---------+-----+-----------+-------------+
|                | Python | StrMath | PEE | Mathparse | InfixParser |
+----------------+--------+---------+-----+-----------+-------------+
| Failures       | 0      | 0       | 61  | 150       | 91          |
| Failures (%)   | 0%     | 0%      | 30% | 75%       | 45%         |
+----------------+--------+---------+-----+-----------+-------------+

In the test above, 198 randomly generated samples were submitted to Python eval() and several other parsing libraries, including strmath. As you can see, the library has 0 failures and almost same speed with native python. You can see test implementation here.

Features

Currently Supported

• basic math operations (+, -, /, //, *, **, %) eg. "2 + 5 * 2" --> 12
• float operations
• braces eg. "(2 + 5) * 2" --> 20
• functions from math module and some builtins

Planned for Future

• custom functions registration
• correct - operator as neg (eg. 50+-30)
• mathematical constants (i.e. PI)

Principle

1. Tokenize expression (split it into operators and numbers)
2. Apply operations order
3. Build evaluation binary tree
4. Evaluate the tree

License

This repository is licensed under MIT license. See LICENSE for details.