从函数中将变量插入全局命名空间？

Question

是否可以编写一个将对象插入全局命名空间并将其绑定到变量的函数？例如:

>>> 'var' in dir()
False
>>> def insert_into_global_namespace():
...        var = "an object"
...        inject var
>>> insert_into_global_namespace()
>>> var
"an object"

Answer 1

它很简单

globals()['var'] = "an object"

和/或

def insert_into_namespace(name, value, name_space=globals()):
    name_space[name] = value

insert_into_namespace("var", "an object")

备注这globals是一个内置关键字,即'globals' in __builtins__.__dict__评估为True.

Answer 2

但请注意,分配声明为全局的函数变量只会注入模块命名空间.导入后,您无法全局使用这些变量:

from that_module import call_that_function
call_that_function()
print(use_var_declared_global)

你明白了

NameError: global name 'use_var_declared_global' is not defined

您必须再次导入以导入那些新的"模块全局变量".内置模块是"真正的全球",但:

class global_injector:
    '''Inject into the *real global namespace*, i.e. "builtins" namespace or "__builtin__" for python2.
    Assigning to variables declared global in a function, injects them only into the module's global namespace.
    >>> Global= sys.modules['__builtin__'].__dict__
    >>> #would need 
    >>> Global['aname'] = 'avalue'
    >>> #With
    >>> Global = global_injector()
    >>> #one can do
    >>> Global.bname = 'bvalue'
    >>> #reading from it is simply
    >>> bname
    bvalue

    '''
    def __init__(self):
        try:
            self.__dict__['builtin'] = sys.modules['__builtin__'].__dict__
        except KeyError:
            self.__dict__['builtin'] = sys.modules['builtins'].__dict__
    def __setattr__(self,name,value):
        self.builtin[name] = value
Global = global_injector()

Answer 3

是的,只需使用该global声明即可.

def func():
    global var
    var = "stuff"

Answer 4

Roland Puntaier 的答案更简洁的版本是：

import builtins

def insert_into_global_namespace():
    builtins.var = 'an object'