is there a better way to check an array?

[jdonnell]

I want to check if a value is in an array. I'm currently doing it as
follows, but I just don't like this way of doing it. It seems
unpythonic.

fieldIsRequired = true
try:
    notRequiredAry.index(k)
    fieldIsRequired = false
except ValueError:
    pass

# throw expception if field is required and is empty
if(product[k] == '' and fieldIsRequired):
    raise GMError(k + ' is required')