I spent part of today writing a very simple network server inPerl. While most of my problems were due to my ignorance, theexperience did give me a new appreciation for introspection andinteractive interpreters.

The problem is that without introspection, things are opaque whensomething goes wrong. What do you have? Certainly not what youexpected, but it's hard to tell much more than that. Withintrospection, you can find out type information, maybe a printablerepresentation of the thing (this gives you some idea

I have a script called ' nsaddrs ', which lists the IP addresses ofthe nameservers for a given domain. It is basically:

addr `dig +short ns $1`

addr is one of my utility programs; it does IP address lookups forhostnames. Normally you give it hostnames on the command line, but forbulk lookups you can give it no arguments and it will read hostnamesfrom standard input, one per line.

Then one day I used nsaddr on a domain that didn't exist and it

Most people doing threading in Python know about Python's GlobalInterpreter Lock (GIL), which causes only one thread to be running inthe CPython interpreter at any one time. This means that threadedcode already has a certain amount of implicit locking going on,making certain operations thread-atomic without you writing explicitlocks.

The important thing about the GIL for this is that it protectsbytecodes, not Python statements . If something happens in a singlebytecode, it's protected; otherwise, you need explicit locking