Why aren't python nested functions called closures?

Question

I have seen and used nested functions in Python, and they match the definition of a closure. So why are they called nested functions instead of closures<

Answer 1

I had a situation where I needed a separate but persistent name space. I used classes. I don't otherwise. Segregated but persistent names are closures.

>>> class f2:
...     def __init__(self):
...         self.a = 0
...     def __call__(self, arg):
...         self.a += arg
...         return(self.a)
...
>>> f=f2()
>>> f(2)
2
>>> f(2)
4
>>> f(4)
8
>>> f(8)
16

# **OR**
>>> f=f2() # **re-initialize**
>>> f(f(f(f(2)))) # **nested**
16

# handy in list comprehensions to accumulate values
>>> [f(i) for f in [f2()] for i in [2,2,4,8]][-1] 
16