# rustshed
[](https://www.python.org/downloads/release/python-3100/)
[](https://codecov.io/gh/pawelrubin/rustshed)
[](https://github.com/pawelrubin/rustshed/blob/main/LICENSE)
A collection of Rust types in Python with complete type annotations.
### Supported Types
- Option
- Result
## Install
```shell
pip install rustshed
```
## Examples
### Option
The `Option` type represents an optional value: every `Option[T]` is either `Some[T]` and contains a value of type `T`, or `Null` (`None` in Rust), and does not.
```Python
from typing import SupportsIndex, TypeVar
from rustshed import Null, Option, Some
T = TypeVar("T")
class SafeList(list[T]):
def get(self, index: SupportsIndex) -> Option[T]:
try:
return Some(self[index])
except IndexError:
return Null
a_list = SafeList([2, 1, 3, 7])
print(a_list.get(1)) # Some(value=1)
print(a_list.get(420)) # Null
```
### Result
The `Result` is the type used for returning and propagating errors: every `Result[T, E]` is either `Ok[T]`, representing success and containing a value of type `T`, or `Err[E]`, representing failure and containing an error of type `E`.
```python
from rustshed import to_result, Result
@to_result[ValueError]
def parse(x: str) -> int:
return int(x)
def multiply(a: str, b: str) -> Result[int, str]:
# try to parse two strings and multiply them
# map a possible error to str
return parse(a).and_then(lambda n: parse(b).map(lambda m: n * m)).map_err(str)
print(multiply("21", "2")) # Ok(value=42)
print(multiply("2!", "2")) # Err(error="invalid literal for int() with base 10: '2!'")
```
### Rust's question mark (?) operator
The question mark (`?`) operator in Rust hides some of the boilerplate of propagating errors up the call stack. Implementing this operator in Python would require changes to the language grammar, hence in **rustshed** it had to be implemented differently.
### Q property
The question mark's functionality has been implemented via the `Q` property (for both `Option` and `Result` types) combined with the `rustshed.result_shortcut` or `rustshed.option_shortcut` decorator.
```python
from rustshed import Ok, Result, to_result, result_shortcut
@to_result[ValueError]
def parse(x: str) -> int:
return int(x)
# explicit early error return with match statements
def try_to_parse_early_return(a: str, b: str) -> Result[int, ValueError]:
match parse(a):
case Ok(value):
x = value
case err:
return err
match parse(b):
case Ok(value):
y = value
case err:
return err
return Ok(x + y)
# early error return using the Q property
@result_shortcut
def try_to_parse(a: str, b: str) -> Result[int, ValueError]:
x = parse(a).Q
y = parse(b).Q
return Ok(x + y)
```
Raw data
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