This transpiler is only working in Python version 3.8.* due to changes in the AST module from 3.9 onwards
PYST is a transpiler between python and Scheme(Racket) source code. It tries to mimic the behavior of CPython and makes simple builtin functions available to the user. It works solely with the Python builtin AST module and does not have any dependencies.
There might still be special edge cases not documented that can cause faulty transpilation. If you come across such a case, please submit the code that did not transpile correctly as an issue here on GitHub or email me privately.
Please install from master (source) if you wish to use all features
- Variables
- Constants
- Arithmetic
- Custom Functions
- Builtins (print, input, range, len; Type converters: int, float, str, bool)
- Types: int, float, str, bool, None, List[{Type}] (Indexing + append, pop and insert), Tuple[{Type, ...}]
- If, elif, else (also nested) (comparators eg.
!===>=andin(for List and Tuple) but notisoris not) - MultiAssign swapping (
seq[n - 1], seq[n] = seq[n], seq[n - 1]) - Augmented assignment (
a += 17) - If expressions (
var = a if b else c) __name__ == '__main__'-> will always be true- For (also nested) (also multi-target e.g.
for i, j in [[0, 1], [2, 3], [4, 5]]:) - While (also nested) (Avoid
while True:asbreakandcontinueare not implemented) - Assert
PYST has a fully fledged typing system and matches types at transpile-time. While most types can dynamically be deduced lists still need to be annotated in the standard python way, for example: myList: List[int] = [1,2,3]. This restriction is necessary because PYST can not infer a type for an empty list. Type annotations are always checked. To create a pending type you may assign a variable to None: var = None. This will make the type pending and allow later assigning of a different value. After a type is determined it may not be changed but can be set to None again. None can act as a nullptr value as in C++ to create optional returns. The variable which has a type but is set to a value of None may still be used like one with a value of its own type, any runtime errors may be avoided by the user (a None check for example: if var != None:).
To avoid undefined behavior during transpilation, you should avoid reassigning the special names: int, float, str, bool, list, print, input, range, len, deepcopy, toList and __{anything}__
PYST tries to make errors as transparent as possible. If a transpilation error is encountered, a clear message explaining it and the exact place it occurred will be presented to the user. For example the following code will result in a transpilation error:
def willError(arg1: List[int]) -> int:
return arg1[17]
my_list: List[float] = [1,2,3]
print(willError(my_list))[TypeError] type <TList: <class 'float'>> can not be applied to argument of type <TList: <class 'int'>>
6>6: print(willError(my_list))
^
Please ensure all paths in all functions return at least None (PYST will implicitly add this return if missing). Multiple return statements in functions must be written so that they are the last executed entity in their function, for example with an if statement:
def testFunc(something: int) -> int:
if something:
return something
else:
return None # This could also be a plain 'return'Note that the else is mandatory here as the first return would fall through to the None return otherwise.
PYST will intentionally fail when an incorrect usage of return could lead to unexpected behavior.
usage: pystranspile [-h] [-version] -input INPUT -output OUTPUT [-exportable]
Transpile simple Python to Scheme(Racket).
optional arguments:
-h, --help show this help message and exit
-version display the current version
-input INPUT path to file that should be transpiled
-output OUTPUT path to file the transpiled code should be saved in
-exportable don't wrap all usercode in a main function to allow easier exports (this might cause extra outputs)
Copyright (C) 2021 Rubin Raithel
You may abbreviate the above mentioned flags to -i, -o, -e and -v.
PYST is installed as a globally available script and does therefore not require the python3 prefix but can still be invoked with it by typing python3 -m pyschemetranspiler.
Please remember that this transpiler only works with Python 3.8.*
There are currently two ways of installing PYST:
Link to PyPi page.
pip install --upgrade pyschemetranspiler
PYST can be installed through a local clone of this repo and the command pip install . (in the cloned repository) which will make the pystranspile command globally available.
PYST is currently licensed under the GPLv3 license.
Copyright (C) 2021 Rubin Raithel