Do I have to cause an ValueError in Python

chars = #some list

try:
    indx = chars.index(chars)
except ValueError:
    #doSomething
else:
   #doSomethingElse

chars = #some list

indx = chars.index(chars)

if indx == -1:
    #doSomething
else:
   #doSomethingElse

if element in mylist:
    index = mylist.index(element)
    # ... do something
else:
    # ... do something else

d = dict((x, loc) for (loc,x) in enumerate(chars))
...
index = d.get(chars_to_find, -1)  # Second argument is default if not found.