pytresult 1.0.1

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result.py

A Python implementation inspired by Rust's Result<T, E>, representing operations that can either succeed (Ok) or fail (Err).

Installation

$ pip install pytresult

Motivation

Using Result helps avoid excessive exception handling and promotes more explicit and robust error handling.

Usage Example

from result import Result, Ok, Err

def divide(a: int, b: int) -> Result[float, str]:
    if b == 0:
        return Err("division by zero")
    return Ok(a / b)

result = divide(10, 2)

if result.is_ok():
    print("Success:", result.unwrap())
else:
    print("Error:", result)  # or result.unwrap_or(0)

Patterns

if let Ok(...) { }

• Rust

  fn divide(a: i32, b: i32) -> Result<f32, String> {
      if b == 0 {
          Err("division by zero".to_string())
      } else {
          Ok(a as f32 / b as f32)
      }
  }
  
  let result = divide(10, 2);
  
  if let Ok(value) = result {
      println!("Success: {}", value);
  }
  

• Python

  from result import Result, Ok, Err
  
  def divide(a: int, b: int) -> Result[int, str]:
      if b == 0:
          return Err("division by zero")
      return Ok(a // b)
  
  result = divide(10, 2)
  
  if r := result.ok():
      assert r is not None
      assert r == 5
  

if let Err(...) { }

• Rust

  fn divide(a: i32, b: i32) -> Result<f32, String> {
      if b == 0 {
          Err("division by zero".to_string())
      } else {
          Ok(a as f32 / b as f32)
      }
  }
  
  let result = divide(10, 0);
  
  if let Err(error) = result {
      println!("Error: {}", error);
  }
  

• Python

  from result import Result, Ok, Err
  
  def divide(a: int, b: int) -> Result[int, str]:
      if b == 0:
          return Err("division by zero")
      return Ok(a // b)
  
  result = divide(10, 0)
  
  if e := result.err():
      assert e is not None
      assert e == "division by zero"
  

Testing

Tests are written using pytest.

To run the tests:

poetry run pytest