Checking number in a list to see if they are beside each other

[perfringo]

I suggest to follow naming conventions set in PEP8 - Function and Variable Names.

Alternative approach could be using zip, set method .difference and built-in function any. This way in process of writing code one can learn much more of Python .

zip is for creating pairs of consecutive numbers without need to worry about IndexError:

>>> nums = [1, 9, 9, 2]
>>> list(zip(nums, nums[1:]))
[(1, 9), (9, 9), (9, 2)]

set method .difference can be used for determining whether elements in pair are equal and match desired value:

>>> set((1, 9)).difference((9,))
{1}
>>> set((9, 9)).difference((9,))
set()

In Python empty means False, so to get True if there is empty set one will use 'not'.

any() is built-in function with short circuiting behaviour.

Therefore function could be written (keyword argument is for cases when we need check numbers other than 9):

>>> def check_list(nums, sentinel=9):
...     return any(not set(pair).difference((sentinel,)) for pair in zip(nums, nums[1:]))
...
>>> check_list([1, 2, 3])
False
>>> check_list([1, 9, 9])
True
>>> check_list([1, 2, 2], sentinel=2)
True

One can use built-in help in interactive interpreter to learn about functions and methods used above (help(zip), help(set.difference), help(any)