can a number preceed a line of code?

[Gribouillis]

is there any case where a line of code that begins with a decimal number expressed as a run of digit characters can be valid Python code in Python3?

These lines are valid python code if that's what you mean

232444
7663 + 12333
87633 >> x

Does your preprocessor remove these lines?

>>> class A:
...     def __rrshift__(self, n):
...         print('Hello', n)
... 
>>> a = A()
>>> 1876 >> a
Hello 1876