I need to understand this concept wherein we can use the dot (.) in the variable name within a function definition. There's no class definition nor a module here and Python is not supposed accept a variable name that includes a dot.
def f(x):
f.author = 'sunder'
f.language = 'Python'
print(x,f.author,f.language)
f(5)
`>>> 5 sunder Python`
Please explain how this is possible, and suggest related documentation for further exploration.
From official documentation:
Programmer’s note: Functions are first-class objects. A “def” statement executed inside a function definition defines a local function that can be returned or passed around. Free variables used in the nested function can access the local variables of the function containing the def.
So, function is an object:
>>> f.__class__
<class 'function'>
>>> f.__class__.__mro__
(<class 'function'>, <class 'object'>)
... and it means that it can store attributes:
>>> f.__dict__
{'language': 'Python', 'author': 'sunder'}
>>> dir(f)
['__annotations__', '__call__', '__class__', '__closure__', '__code__', '__defaults__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__get__', '__getattribute__', '__globals__', '__gt__', '__hash__', '__init__', '__kwdefaults__', '__le__', '__lt__', '__module__', '__name__', '__ne__', '__new__', '__qualname__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'author', 'language']
fmust have been defined earlier.AttributeError: 'function' object has no attribute 'name'.