<img src="https://raw.githubusercontent.com/tobias-kirschstein/silberstral/master/img/logo.png" width="150px"> Silberstral
===========
>Reveal the true shape of type vars
[//]: # (For more badges visit https://shields.io/)
[](https://pypi.org/project/silberstral/)
[](https://pypi.org/project/silberstral/)
Python's typing system is weak and lacks features well known in other languages.
For example, templating in C++ allows you to instantiate a new object of the templated class `T` via `T(..)` which is not possible in Python.
The **Silberstral** package provides remedy with a simple utility to obtain the actual *type* that a generic type var refers to:
#### C++
```cpp
template<typename T>
class DefaultContainer {
T get(int idx) {
defaultElement = T(); // <- in C++, we can access the actual class of T
...
}
}
```
#### Python
```python
_T = TypeVar('_T')
class DefaultContainer(Generic[_T]):
def get(self, idx: int) -> _T:
default_element = _T() # <- DOES NOT WORK
...
```
#### Python + Silberstral
```python
from silberstral import reveal_type_var
_T = TypeVar('_T')
class DefaultList(Generic[_T]):
def get(self, idx: int) -> _T:
T_cls = reveal_type_var(self, _T) # <- Reveals the actual class of _T, e.g., int, str, ...
default_element = T_cls()
...
```
## Installation
The package is available at [pypi](https://pypi.org/project/silberstral/):
```commandline
pip install silberstral
```
## Usage
`reveal_type_var(obj_or_cls, type_var)`: Finds the actual type that `type_var` was instantiated to in `obj_or_cls`.
Example:
```python
from typing import TypeVar, Generic
from silberstral import reveal_type_var
_T = TypeVar('_T')
class List(Generic[_T]):
pass
reveal_type_var(List[int], _T)
>>> int
str_list = List[str]()
reveal_type_var(str_list, _T)
>>> str
```
---
`reveal_type_vars(obj_or_cls)`: Lists all type vars and their corresponding instantiations of `obj_or_cls`
Example:
```python
from typing import TypeVar, Generic
from silberstral import reveal_type_vars
_K = TypeVar('_K')
_V = TypeVar('_V')
class Dict(Generic[_K, _V]):
pass
reveal_type_vars(Dict[int, str])
>>> {_K: int, _V: str}
```
---
`is_type_var_instantiated(obj_or_cls, type_var)`: Checks whether `type_var` was instantiated with an actual class in `obj_or_cls`
Example:
```python
from typing import TypeVar, Generic
from silberstral import is_type_var_instantiated
_T = TypeVar('_T')
class List(Generic[_T]):
pass
is_type_var_instantiated(List, _T)
>>> False
is_type_var_instantiated(List[int], _T)
>>> True
```
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"description": "\n<img src=\"https://raw.githubusercontent.com/tobias-kirschstein/silberstral/master/img/logo.png\" width=\"150px\"> Silberstral\n===========\n>Reveal the true shape of type vars\n\n[//]: # (For more badges visit https://shields.io/)\n[](https://pypi.org/project/silberstral/)\n[](https://pypi.org/project/silberstral/)\n\nPython's typing system is weak and lacks features well known in other languages. \nFor example, templating in C++ allows you to instantiate a new object of the templated class `T` via `T(..)` which is not possible in Python.\nThe **Silberstral** package provides remedy with a simple utility to obtain the actual *type* that a generic type var refers to:\n\n#### C++\n```cpp\ntemplate<typename T>\nclass DefaultContainer {\n \n T get(int idx) {\n defaultElement = T(); // <- in C++, we can access the actual class of T\n ...\n }\n \n}\n```\n#### Python\n```python\n_T = TypeVar('_T')\nclass DefaultContainer(Generic[_T]):\n \n def get(self, idx: int) -> _T:\n default_element = _T() # <- DOES NOT WORK\n ...\n```\n\n#### Python + Silberstral\n\n```python\nfrom silberstral import reveal_type_var\n\n_T = TypeVar('_T')\nclass DefaultList(Generic[_T]):\n \n def get(self, idx: int) -> _T:\n T_cls = reveal_type_var(self, _T) # <- Reveals the actual class of _T, e.g., int, str, ...\n default_element = T_cls()\n ...\n```\n\n## Installation\nThe package is available at [pypi](https://pypi.org/project/silberstral/):\n```commandline\npip install silberstral\n```\n\n## Usage\n`reveal_type_var(obj_or_cls, type_var)`: Finds the actual type that `type_var` was instantiated to in `obj_or_cls`.\n\nExample:\n```python\nfrom typing import TypeVar, Generic\nfrom silberstral import reveal_type_var\n\n_T = TypeVar('_T')\nclass List(Generic[_T]):\n pass\n\nreveal_type_var(List[int], _T)\n>>> int\n\nstr_list = List[str]()\nreveal_type_var(str_list, _T)\n>>> str\n```\n---\n`reveal_type_vars(obj_or_cls)`: Lists all type vars and their corresponding instantiations of `obj_or_cls`\n\nExample:\n```python\nfrom typing import TypeVar, Generic\nfrom silberstral import reveal_type_vars\n\n_K = TypeVar('_K')\n_V = TypeVar('_V')\nclass Dict(Generic[_K, _V]):\n pass\n\nreveal_type_vars(Dict[int, str])\n>>> {_K: int, _V: str}\n```\n---\n`is_type_var_instantiated(obj_or_cls, type_var)`: Checks whether `type_var` was instantiated with an actual class in `obj_or_cls`\n\nExample:\n\n```python\nfrom typing import TypeVar, Generic\nfrom silberstral import is_type_var_instantiated\n\n_T = TypeVar('_T')\nclass List(Generic[_T]):\n pass\n\nis_type_var_instantiated(List, _T)\n>>> False\n\nis_type_var_instantiated(List[int], _T)\n>>> True\n```\n",
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