"""Utilities for generating code at runtime."""
from typing import Any, Callable, Dict, List
__all__ = [
'Function',
'Method',
'InitMethod',
'HashMethod',
'CompareMethod',
'EqMethod',
]
MISSING = object()
[docs]def Function(name: str,
args: List[str],
body: List[str],
*,
globals: Dict[str, Any] = None,
locals: Dict[str, Any] = None,
return_type: Any = MISSING,
argsep: str = ', ') -> Callable:
assert locals is not None
return_annotation = ''
if return_type is not MISSING:
locals['_return_type'] = return_type
return_annotation = '->_return_type'
bodys = '\n'.join(f' {b}' for b in body)
src = f'def {name}({argsep.join(args)}){return_annotation}:\n{bodys}'
exec(src, globals, locals)
obj = locals[name]
obj.__sourcecode__ = src
return obj
[docs]def Method(name: str,
args: List[str],
body: List[str],
**kwargs: Any) -> Callable:
return Function(name, ['self'] + args, body, **kwargs)
[docs]def InitMethod(args: List[str],
body: List[str],
**kwargs: Any) -> Callable[[], None]:
return Method('__init__', args, body, return_type='None', **kwargs)
[docs]def HashMethod(attrs: List[str], **kwargs: Any) -> Callable[[], None]:
self_tuple = obj_attrs_tuple('self', attrs)
return Method('__hash__',
[],
[f'return hash({self_tuple})'],
**kwargs)
[docs]def EqMethod(fields: List[str], **kwargs: Any) -> Callable[[], None]:
return CompareMethod(name='__eq__', op='==', fields=fields, **kwargs)
[docs]def CompareMethod(name: str,
op: str,
fields: List[str],
**kwargs: Any) -> Callable[[], None]:
# Generate object comparison function (__eq__, __le__, __gt__, etc.)
# Examples:
# The example:
#
# CompareMethod(
# name='__eq__',
# op='==',
# fields=['x', 'y'],
# )
#
# Generates a method like this:
#
# def __eq__(self, other):
# if other.__class__ is self.__class__:
# return (self.x,self.y) == (other.x,other.y)
# return NotImplemented
self_tuple = obj_attrs_tuple('self', fields)
other_tuple = obj_attrs_tuple('other', fields)
return Method(name,
['other'],
['if other.__class__ is self.__class__:',
f' return {self_tuple}{op}{other_tuple}',
'return NotImplemented'],
**kwargs)
def obj_attrs_tuple(obj_name: str, attrs: List[str]) -> str:
# if attrs is ['x', 'y'] and obj_name is 'self',
# returns '(self.x,self.y)'.
if not attrs:
return '()'
return f'({",".join([f"{obj_name}.{f}" for f in attrs])},)'
