locals are not passed to inner function defined in exec()

[sinoleao-1]

Bug report

A clear and concise description of what the bug is.
Include a minimal, reproducible example (https://stackoverflow.com/help/minimal-reproducible-example), if possible.

With following code, f1 is OK, but f2 failed with the error "name 'a' is not defined"

 def f1():
    a = "hello"
    exec("print(a)")
 
 def f2():
    a = "hello"
    exec("def inner(): print(a)\ninner()")
 
 f1()
 f2()

Your environment

• CPython versions tested on:
  Python 3.5.2 (default, Aug 10 2017, 23:51:58)
  [GCC 4.4.3] on linux

• Operating system and architecture:
  Linux 3.10.0-1160.25.1.el7.x86_64

[sinoleao-1]

Did the investigation with the code below, looks like the code executed by exec() inherits locals and globals from its caller method. The inner method can inherit globals further, but cannot inherit locals.

def f1():
   a = "hello"
   exec("print('locals:', str(locals()))")
   exec("print('globals:', str(list(globals().keys())))")

def f2():
   a = "hello"
   exec("def inner():print('locals:', str(locals()))\ninner()")
   exec("def inner():print('globals:', str(list(globals().keys())))\ninner()")

if __name__ == '__main__':
   f1()
   f2()

output:
locals: {'a': 'hello'}
globals: ['__file__', '__builtins__', '__loader__', '__name__', '__package__', '__spec__', '__cached__', '__doc__', 'f1', 'f2']
locals: {}
globals: ['__file__', '__builtins__', '__loader__', '__name__', '__package__', '__spec__', '__cached__', '__doc__', 'f1', 'f2']

[sweeneyde]

I think this behavior is explained by the docs in the following sentence:

If exec gets two separate objects as globals and locals, the code will be executed as if it were embedded in a class definition.

The behavior you notice is consistent with that:

class Somthing:
    a = "hello"
    def inner():
        print(a)
    inner()

# result: NameError: name 'a' is not defined

[sweeneyde]

It looks like that language was added in commit 83efd6c for issue #57766

@terryjreedy, do you think this needs further clarification in the docs? I could see how this text at the top of the paragraph could be misleading:

In all cases, if the optional parts are omitted, the code is executed in the current scope.

[sweeneyde]

Closing as a duplicate of #68988.