How to make DNS queries on Linux (with python) bypassing nsswitch.conf and no additional packages

I'd like to make DNS queries to check if some entries in the /etc/hosts file are obsolete (now working DNS) or conflicting with DNS answers. nsswitch.conf is configured to lookup /etc/hosts first. gethostbyname() or getaddrinfo() will not work because they both use the OSes mechasnims (nsswitch.conf).

I know about the pythonDNS package. Unfortunatly it's rather difficult to install 开发者_如何学Goadditional packages on the systems. Also, the python version available is rather old (python23).

The only possible solution I see so far is parsing nslookup or dig output. But I really don't like the idea because of the complexity involved (CNAMEs, multiple records,...).

I'm searching for a single class/function solution to make DNS A-Record Lookups.

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The obvious options:

• PyDNS
• dnspython
• Call res_query via the libresolv C API (e.g. using ctypes)

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Twisted Names contains a DNS client.

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I always liked evdns

http://linux.die.net/man/3/evdns

There appears to be a python binding called pyevent

http://code.google.com/p/pyevent/source/browse/trunk/evdns.pxi?r=44

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Is it impossible to install additional software because of technical limitations or because of policy?

If it's not policy you might be able to get somewhere with virtualenv