Programming Python, 3rd Edition

Generating Forward-Link Web Pages

Moving is rarely painless, even in the brave new world of cyberspace. Changing your web site’s Internet address can lead to all sorts of confusion. You need to ask known contacts to use the new address, and hope that others will eventually stumble onto it themselves. But if you rely on the Internet, moves are bound to generate at least as much confusion as an address change in the real world.

Unfortunately, such site relocations are often unavoidable. Both Internet Service Providers (ISPs) and server machines come and go over the years. Moreover, some ISPs let their service fall to intolerably low levels; if you are unlucky enough to have signed up with such an ISP, there is not much recourse but to change providers, and that often implies a change of web addresses.^[*]

Imagine, though, that you are an O’Reilly author and have published your web site’s address in multiple books sold widely all over the world. What do you do when your ISP’s service level requires a site change? Notifying the tens or hundreds of thousands of readers out there isn’t exactly a practical solution.

Probably the best you can do is to leave forwarding instructions at the old site for some reasonably long period of time—the virtual equivalent of a “We’ve Moved” sign in a storefront window. On the Web, such a sign can also send visitors to the new site automatically: simply leave a page at the old site containing a hyperlink to the page’s address at the new site. With such ...