Innerscope

innerscope exposes the inner scope of functions and offers primitives suitable for creating pipelines. It explores a design space around functions, dictionaries, and classes.

To install: pip install innerscope

A function can be made to act like a dictionary:

@innerscope.call
def info():
    first_name = 'Erik'
    last_name = 'Welch'
    full_name = f'{first_name} {last_name}'
    return 'success!'

>>> info['first_name']
'Erik'
>>> info['full_name']
'Erik Welch'
>>> info.return_value
'success!'

Sometimes we want functions to be more functional and accept arguments:

if is_a_good_idea:
    suffix = 'the amazing'
else:
    suffix = 'the bewildering'

@innerscope.callwith(suffix)
def info_with_suffix(suffix=None):
    first_name = 'Erik'
    last_name = 'Welch'
    full_name = f'{first_name} {last_name}'
    if suffix:
        full_name = f'{full_name} {suffix}'

>>> info_with_suffix['full_name']
'Erik Welch the bewildering'

Cool!

But, what if we want to reuse the data computed in info? We can control exactly what values are within scope inside of a function (including from closures and globals; more on these later). Let's bind the variables in info to a new function:

@info.bindto
def add_suffix(suffix):
    full_name = f'{first_name} {last_name} {suffix}'

>>> scope = add_suffix('the astonishing')
>>> scope['full_name']
'Erik Welch the astonishing'

add_suffix here is a ScopedFunction. It returns a Scope, which is the dict-like object we've already seen.

scoped_function ftw!

Except for the simplest tasks (as with call and callwith above), using scoped_function should usually be preferred.

# step1 becomes a ScopedFunction that we can call
@scoped_function
def step1(a):
    b = a + 1

>>> scope1 = step1(1)
>>> scope1 == {'a': 1, 'b': 2}
True

# Bind any number of mappings to variables (later mappings have precedence)
@scoped_function(scope1, {'c': 3})
def step2(d):
    e = max(a + d, b + c)

>>> step2.outer_scope == {'a': 1, 'b': 2, 'c': 3}
True
>>> scope2 = step2(4)
>>> scope2 == {'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}
True
>>> scope2.inner_scope == {'d': 4, 'e': 5}
True

Suppose you're paranoid (like me!) and want to control whether a function uses values from closures or globals. You're in luck!

global_x = 1

def f():
    closure_y = 2
    def g():
        local_z = global_x + closure_y
    return g

# If you're the trusting type...
>>> g = f()
>>> innerscope.call(g) == {'global_x': 1, 'closure_y': 2, 'local_z': 3}
True

# And for the intelligent...
>>> paranoid_g = scoped_function(g, use_closures=False, use_globals=False)
>>> paranoid_g.missing
{'closure_y', 'global_x'}
>>> paranoid_g()

- NameError: Undefined variables: 'global_x', 'closure_y'.
- Use `bind` method to assign values for these names before calling.

>>> new_g = paranoid_g.bind({'global_x': 100, 'closure_y': 200})
>>> new_g.missing
set()
>>> new_g() == {'global_x': 100, 'closure_y': 200, 'local_z': 300}
True

How?

This library does not use exec, eval, the AST, or source code. It runs on CPython, PyPy, and Stackless Python. You should feel comfortable using innerscope. It actually offers two methods for obtaining the inner scope, and both are very reliable. Of course we're doing something magical under the hood, and I would love to explain how some day.

Why?

It's all @mrocklin's fault for asking a question. innerscope is exploring a data model that could be convenient for running code remotely with dask. I bet it would even be useful for building pipelines with dask. I'm sure there are other creative uses for it just waiting to be discovered.

This library is totally awesome and you should use it and tell all your friends 😉 !