fparse.py

fparse.py

import ctypes
import inspect
from parse import parse

def fparse(template, string):
    parent_frame = inspect.currentframe().f_back
    parent_frame.f_locals.update(parse(template, string).named)
    ctypes.pythonapi.PyFrame_LocalsToFast(
        ctypes.py_object(parent_frame),
        ctypes.c_int(0),
    )

fparse_example.py

# It works at the top level of a module
>>> from fparse import fparse
>>> fparse('The {animal} jumped over the {celestial_body}', 'The cow jumped over the moon')
>>> animal
'cow'
>>> celestial_body
'moon'

function_example.py

# It works inside of a function, but the names must be pre-defined.
# This only works because of the `PyFrame_LocalsToFast` call.
# Without it, the names don't make it into the function scope.
>>> def in_a_function():
...     animal = None
...     celestial_body = None
...     fparse('The {animal} jumped over the {celestial_body}', 'The cow jumped over the moon')
...     print(animal, celestial_body)
...
>>> in_a_function()
cow moon

function_example2.py

# If you don't pre-define the names,
# the function appears to work.
>>> def in_another_function():
...     fparse('The {animal} jumped over the {celestial_body}', 'The cow jumped over the moon')
...     return locals()
...
>>> in_another_function()
{'animal': 'cow', 'celestial_body': 'moon'}

function_example3.py

# However it does not.
# Instead, we get a `NameError`.
# As far as I'm aware, there's no way to make this work.
>>> def in_a_third_function():
...     fparse('The {animal} jumped over the {celestial_body}', 'The cow jumped over the moon')
...     print(animal, celestial_body)
...
>>> in_a_third_function()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in in_a_third_function
NameError: name 'animal' is not defined