Chunk + Enumerate a list of digits
Python 3.8 (pre-release), 41 bytes



lambda l,n=0:[n:=n+(l!=(l:=x))for x in l]


Try it online!

Praise the magic walrus := of assignment expressions.



Python 2, 42 bytes



n=0
for x in input():n+=x!=id;id=x;print n


Try it online!