Tell the compiler about a local one that he doesn't know about?

Question

I have a function called letthat changes the namespace of callers to insert a new variable.

def let(**nameValuePair):
    from inspect import stack

    name, value = nameValuePair.items()[0]
    stack()[1][0].f_locals[name] = value
    return value

The idea is that you can insert assignment operators anywhere, even if assignment statements are usually not allowed in Python (although let()5 extra characters are required.

This works great when called from a global namespace.

>>> let(outside = 'World')
>>> print(outside)
World

This does not fail NameError: global name 'hello' is not defined:

>>> def breaker():
...     let(hello = 'World')
...     print(hello)
...
>>> breaker()

You can come to the conclusion that the problem is related to my function let. It is not - my function works fine. To show you that:

>>> def fine():
...     let(another = 'World')
...     print(locals()['another'])
...
>>> fine()
World

, Python breaker. , , , breaker, let, dis.

>>> def normal():
...     hello = 'World'
...     print(hello)
...
>>> normal()
World

>>> from dis import dis
>>> print(dis(normal))
 0 LOAD_CONST               1 ('World')
 3 STORE_FAST               0 (hello)
 6 LOAD_FAST                0 (hello)
 9 PRINT_ITEM
10 PRINT_NEWLINE
11 LOAD_CONST               0 (None)
14 RETURN_VALUE

>>> print(dis(breaker))
 0 LOAD_GLOBAL              0 (let)
 3 LOAD_CONST               1 ('hello')
 6 LOAD_CONST               2 ('World')
 9 CALL_FUNCTION          256
12 POP_TOP
13 LOAD_GLOBAL              2 (hello)  # <= This is the real problem.
16 PRINT_ITEM
17 PRINT_NEWLINE
18 LOAD_CONST               0 (None)
19 RETURN_VALUE

, breaker, , hello , .

? , , , , , :

LOAD_GLOBAL 1 (locals)
CALL_FUNCTION 0
LOAD_CONST 1 ('hello')  # Or whatever the name of the variable is
BINARY_SUBSCR

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• , .
• -, . ( , ).

... , , STORE_GLOBAL DELETE_GLOBAL RETURN_VALUE, ? - - ?

Answer 1

locals() :

; , .

inspect f_locals, , .

Answer 2

: . 3.x, 2.x, , . , . , python.

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