Adding to the PATH but not if already in $PATH

I want to prepend a directory to my PATH in my $HOME/.bashrc and export the result. But I only want it to happen once: iow, if a directory I want prepended is already in the PATH, do not prepend it again. Something like: if "/home/dw/bin" not in $PATH ; then PATH=/home/dw:$PATH export

Adding to the PATH but not if already in $PATH

I want to prepend a directory to my PATH in my $HOME/.bashrc and export the result. But I only want it to happen once: iow, if a directory I want prepended is already in the PATH, do not prepend it again. Something like: if "/home/dw/bin" not in $PATH ; then PATH=/home/dw:$PATH export