def exec(*args, **kwargs): # real signature unknown
    """
    Execute the given source in the context of globals and locals.
    
    The source may be a string representing one or more Python statements
    or a code object as returned by compile().
    The globals must be a dictionary and locals can be any mapping,
    defaulting to the current globals and locals.
    If only globals is given, locals defaults to it.
    """
    pass

a=10
#exec("a+=10",{"a": 30})
exec("a+=10",None)#这样写，a是全局？还是局部变量？为什么？
print(a)

a=10
exec("a+=10",{"a": 30})# 这样写，a是全局？还是局部变量？为什么？
#exec("a+=10",None)
print(a)

--
FROM 120.242.240.*