On Aug 25, 2:33 pm, Evan Driscoll <eva...@gmail.com> wrote:
> I want to make a context manager that will temporarily change the
> value of a variable within the scope of a 'with' that uses it. This is
> inspired by a C++ RAII object I've used in a few projects. Ideally,
> what I want is something like the following:
Okay, so I think I actually got this with some consultation with a
friend. Critiques?
from contextlib import contextmanager
import inspect
def get_parents_var(offset, var):
f = inspect.stack()[offset][0]
if var in f.f_locals:
return f.f_locals[var]
else:
return f.f_globals[var]
def set_parents_var(offset, var, val):
f = inspect.stack()[offset][0]
if var in f.f_locals:
f.f_locals[var] = val
elif var in f_globals:
f.f_globals[var] = val
else:
assert False
@contextmanager
def changed_value_tb(var_name, temp_value):
# 1 is here, 2 will be the implicit next() function, 3 is the
real caller
offset = 3
old_value = get_parents_var(offset, var_name)
set_parents_var(offset, var_name, temp_value)
try:
yield None
finally:
set_parents_var(offset, var_name, old_value)
x = 5
print x # prints 5
with changed_value_tb("x", 10):
print x # prints 10
print x # prints 5
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