In [54]: def TopLevel(a):
    ...:     lastLimit = 3 # kimit on length of lastvalues
    ...:     lastvalues = [0 for i in range(0,lastLimit)]
    ...:     def Closure(b,reset=False):
    ...:         if reset:
    ...:             for index in range(0,len(lastvalues)):
    ...:                 lastvalues[index] = 0
    ...:                 # reconstructing lastvalues would require a nonlocal
    ...:                 # declaration because it would build a different list
    ...:         print('DEBUG Closure lastvalues', type(lastvalues), lastvalues)
    ...:         some = a + b + sum(lastvalues)
    ...:         lastvalues.pop(0) # returns and discards element at the front
    ...:         lastvalues.append(b) # append onto the back
    ...:         return some
    ...:     return Closure

In [54]: def TopLevel(a):
    ...:     lastLimit = 3 # kimit on length of lastvalues
    ...:     lastvalues = [0 for i in range(0,lastLimit)]
    ...:     def Closure(b,reset=False):
    ...:         nonlocal lastvalues
    ...:         if reset:
    ...:             lastvalues = [0 for i in range(0,lastLimit)]
    ...:         print('DEBUG Closure lastvalues', type(lastvalues), lastvalues)
    ...:         some = a + b + sum(lastvalues)
    ...:         lastvalues.pop(0) # returns and discards element at the front
    ...:         lastvalues.append(b) # append onto the back
    ...:         return some
    ...:     return Closure
    
    In [239]: def TopLevel(a):
     ...:     lastLimit = 3 # kimit on length of lastvalues
     ...:     lastvalues = [0 for i in range(0,lastLimit)]
     ...:     def Closure(b,reset=False):
     ...:         if reset:
     ...:             for index in range(0,len(lastvalues)):
     ...:                 lastvalues[index] = 0
     ...:                 # reconstructing lastvalues would require a nonlocal
     ...:                 # declaration because it would build a different list
     ...:         print('DEBUG Closure lastvalues', type(lastvalues), lastvalues)
     ...:         some = a + b + sum(lastvalues)
     ...:         lastvalues.pop(0) # returns and discards element at the front
     ...:         lastvalues.append(b) # append onto the back
     ...:         return some
     ...:     def grow(newLimit):
     ...:         nonlocal lastLimit
     ...:         if newLimit < 1:
     ...:             raise ValueError('INVALID newLimit ' + str(newLimit))
     ...:         while len(lastvalues) > newLimit:
     ...:             lastvalues.pop(0)
     ...:         while len(lastvalues) < newLimit:
     ...:             lastvalues.append(0)
     ...:         lastLimit = newLimit
     ...:     return (Closure, grow)
     
     In [321]: def TopLevel(a):
     ...:     lastLimit = 3 # kimit on length of lastvalues
     ...:     lastvalues = [0 for i in range(0,lastLimit)]
     ...:     def Closure(b,reset=False,grower=None):
     ...:         nonlocal lastLimit
     ...:         if grower != None and grower != lastLimit:
     ...:             if grower < 0:
     ...:                 raise ValueError('INVALID newLimit ' + str(grower))
     ...:             while len(lastvalues) > grower:
     ...:                 lastvalues.pop(0)
     ...:             while len(lastvalues) < grower:
     ...:                 lastvalues.append(0)
     ...:             lastLimit = grower
     ...:         if reset:
     ...:             for index in range(0,len(lastvalues)):
     ...:                 lastvalues[index] = 0
     ...:                 # reconstructing lastvalues would require a nonlocal
     ...:                 # declaration because it would build a different list
     ...:         print('DEBUG Closure lastvalues', type(lastvalues), lastvalues)
     ...:         some = a + b + sum(lastvalues)
     ...:         lastvalues.append(b) # append onto the back
     ...:         lastvalues.pop(0) # returns and discards element at the front
     ...:         print('DEBUG lastLimit grower ' + str(lastLimit) + ' ' + str(grower))
     ...:         return some
     ...:     return Closure
     
     In [322]: def genA(a):
     ...:     for value in range(0,a):
     ...:         yield(value)
     ...:

In [323]: ga = genA(10)

In [324]: type(ga)
Out[324]: generator

In [325]: ga
Out[325]: <generator object genA at 0x7fae98d13220>

In [326]: for value in ga:
     ...:     print(value)
     ...:
0
1
2
3
4
5
6
7
8
9

In [327]: list(genA(10))
Out[327]: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

In [328]: ga = genA(10)

In [329]: ga
Out[329]: <generator object genA at 0x7fae98578660>

In [330]: ga.__next__()
Out[330]: 0

In [331]: ga.__next__()
Out[331]: 1

In [332]: ga.__next__()
Out[332]: 2

In [333]: ga.__next__()
Out[333]: 3

In [334]: ga.__next__()
Out[334]: 4

In [335]: ga.__next__()
Out[335]: 5

In [336]: ga.__next__()
Out[336]: 6

In [337]: ga.__next__()
Out[337]: 7

In [338]: ga.__next__()
Out[338]: 8

In [339]: ga.__next__()
Out[339]: 9

In [340]: ga.__next__()
---------------------------------------------------------------------------
StopIteration                             Traceback (most recent call last)
Cell In[340], line 1
----> 1 ga.__next__()

StopIteration:

In [341]: ga = genA(10)

In [342]: for value in ga:
     ...:     print(value)
     ...:
0
1
2
3
4
5
6
7
8
9

In [344]: def genA(a):
     ...:     for value in range(0,a):
     ...:         yield(value)
     ...:         if value > 7:
     ...:             return
     ...: