py-evalexpr

py_evalexpr

A Python extension module written in Rust that provides bindings to the evalexpr crate for expression evaluation.

🌟 Features

• 🧮 Evaluate mathematical and logical expressions from Python
• 🔒 Three evaluation contexts:
  • StatelessContext: Simple expressions without variables
  • ImmutableContext: Expressions with predefined variables
  • MutableContext: Expressions that can update variables
• 📊 Type-specific evaluation methods for:
  • Integers
  • Floats
  • Strings
  • Booleans
  • Tuples
• ⚡ High-performance expression evaluation
• 🚀 Built using Rust's evalexpr crate (version 12.0.2)
• 🐍 Python bindings via PyO3

⚡ Performance Benchmarks

PyEvalExpr was benchmarked against several popular Python expression evaluation libraries:

Test Case	py_evalexpr	sympy	asteval	simpleeval
simple_arithmetic	0.0047 ms	0.2339 ms	0.0116 ms	0.0083 ms
complex_arithmetic	0.0066 ms	0.2329 ms	0.0186 ms	0.0118 ms
variables	0.0046 ms	0.1996 ms	0.0126 ms	0.0083 ms
math_functions	0.0077 ms	0.2403 ms	0.0230 ms	0.0117 ms
complex_expression	0.0095 ms	0.2268 ms	0.0244 ms	0.0141 ms
boolean_logic	0.0059 ms	N/A	0.0159 ms	0.0103 ms

Benchmarks performed on AMD Ryzen 9 7950X with 32GB RAM running Python 3.11 using 50,000 iterations per test. Lower is better.

🔧 Prerequisites

• Python 3.11 or higher
• Rust toolchain (cargo, rustc)
• Compatible C compiler

📦 Installation

pip install py-evalexpr

💡 Usage Examples

Quick Evaluation

from py_evalexpr import evaluate, evaluate_int, evaluate_float

# Basic arithmetic
result = evaluate("2 + 3 * 4")         # Returns 14
result = evaluate("sqrt(16) + 2")      # Returns 6.0

# Type-specific evaluation
int_val = evaluate_int("42")           # Returns 42 as int
float_val = evaluate_float("3.14159")  # Returns 3.14159 as float
bool_val = evaluate_boolean("5 > 3")   # Returns True

Context Usage

Stateless Context

from py_evalexpr import StatelessContext

context = StatelessContext()
result = context.evaluate("42").value          # Integer: 42
result = context.evaluate("sin(0.5)").value    # Uses built-in math functions

Immutable Context

from py_evalexpr import ImmutableContext

context = ImmutableContext()
context.variables["x"] = 10
context.variables["y"] = 20

result = context.evaluate("x + y").value       # Returns 30

Mutable Context

from py_evalexpr import MutableContext

context = MutableContext()
context.evaluate_empty("x = 10")
context.evaluate_empty("y = 20")
context.evaluate_empty("sum = x + y")
result = context.evaluate("sum * 2").value     # Returns 60

🛡️ Error Handling

from py_evalexpr import evaluate
from py_evalexpr.exceptions import EvaluationError

try:
    result = evaluate("undefined_var + 5")
except EvaluationError as e:
    print(f"Evaluation error: {e}")

🤝 Contributing

Contributions are welcome:

• Open an issue to discuss proposed changes
• Submit pull requests
• Follow existing code style

🙏 Acknowledgments

• evalexpr - Rust crate that powers this project
• PyO3 - Python extensions framework
• maturin - Python packaging tool
• devbox - Predictable development environments
• uv - Python package installer

Made in 🇨🇦🍁 by Benjamin Kiiskila