python - Replacing list item with contents of another list

Question

Similar to this question, but instead of replacing one item with another, I'd like to replace any occurrences of one item with the contents of a list.

orig = [ 'a', 'b', 'c', 'd', 'c' ]
repl = [ 'x', 'y', 'z' ]
desired = [ 'a', 'b', 'x', 'y', 'z', 'd', 'x', 'y', 'z' ]

# these are all incorrect, or fail to compile
[ repl if x == 'c' else x for x in orig ]
[ [a for a in orig] if x == 'c' else x for x in orig ]
[ (a for a in orig) if x == 'c' else x for x in orig ]
[ a for a in orig if x == 'c' else x for x in orig ]

Edit: made it clear I meant to replace all occurrences of the item, rather than just the first. (Apologies to anyone who didn't cover that case in their answer.)

Answer 1

>>> orig = [ 'a', 'b', 'c', 'd' ]
>>> repl = [ 'x', 'y', 'z' ]
>>> desired = list(orig)  #can skip this and just use `orig` if you don't mind modifying it (and it is a list already)
>>> desired[2:3] = repl
>>> desired
['a', 'b', 'x', 'y', 'z', 'd']

And of course, if you don't know that 'c' is at index 2, you can use orig.index('c') to find out that information.