Py3DNS - Python 3 DNS library

4.0.2 · active · verified Fri Apr 17

Py3DNS is a Python 3 library for making DNS queries and parsing responses. It provides a flexible API for various record types (A, AAAA, MX, NS, SOA, etc.) and is a port of the older `pydns` library, specifically adapted for Python 3. The current version is 4.0.2, with updates primarily focusing on Python compatibility, bug fixes, and feature enhancements like `asyncio` support.

Common errors

```
ModuleNotFoundError: No module named 'DNS'
```
cause This error typically occurs if `py3dns` is not installed, or if an attempt was made to install the Python 2-only `pydns` package instead.

fix Verify that `py3dns` is installed in your active environment by running `pip install py3dns`. Ensure your Python interpreter matches the environment where `py3dns` is installed.
```
DNSError: No name servers specified
```
cause The library could not find or was not explicitly provided with any DNS name server addresses to send queries to, often because `DNS.DiscoverNameServers()` was not called or failed.

fix Before making any `DNS.Request`, ensure name servers are set up by calling `DNS.DiscoverNameServers()`, `DNS.ParseResolvConf()`, or by manually setting `DNS.defaults['server'] = ['IP_ADDRESS_1', 'IP_ADDRESS_2']`.
```
socket.timeout: timed out
```
cause A DNS query took longer than the default or configured timeout period, often due to network issues, an unresponsive DNS server, or a very slow connection.

fix Increase the timeout value by setting `DNS.defaults['timeout'] = X` (where `X` is the timeout in seconds) before making the request. Also, check your network connectivity and the availability of your configured DNS servers.

Warnings

breaking Direct migration from Python 2's 'pydns' to 'py3dns' is not straightforward, as 'py3dns' is a separate project with Python 3 specific adjustments. While the API is largely compatible, code will require Python 3 syntax and 'py3dns' installation.
Fix: Ensure `py3dns` is installed (`pip install py3dns`). Review your existing `pydns` code and adjust for Python 3 syntax and module differences. Test thoroughly.
gotcha DNS queries will fail with a 'No name servers specified' error if name servers are not explicitly configured or automatically discovered before making requests.
Fix: Call `DNS.DiscoverNameServers()` or `DNS.ParseResolvConf()` before making any `DNS.Request` calls to ensure name servers are properly set up. Alternatively, set `DNS.defaults['server'] = ['your_dns_server_ip']`.
gotcha Synchronous DNS requests (e.g., `DNS.Request.req()`) are blocking and can lead to performance bottlenecks or frozen applications in concurrent or I/O-bound environments.
Fix: For concurrent or non-blocking operations, consider using Py3DNS's `asyncio` integration (e.g., `DNS.async_req`) introduced in version 4.0.0, or manage concurrency using Python's `threading` or `multiprocessing` modules.

Install

pip install py3dns Install Py3DNS

Imports

DNS
wrong:
```
from py3dns import DNS
```
correct:
```
import DNS
```
The primary API is exposed directly under the 'DNS' module namespace after 'import DNS'.

Quickstart

This quickstart demonstrates how to perform basic A and MX record DNS queries using Py3DNS. It includes name server discovery and a fallback to public DNS if discovery fails, making the example robust for various environments.

import DNS
import os

# Configure name servers, typically from system settings
# For testing, you can explicitly set them or rely on system discovery
# Example using Google's DNS for demonstration if system discovery fails or for specific testing
# DNS.defaults['server'] = ['8.8.8.8', '8.8.4.4']

# Discover name servers from /etc/resolv.conf or common system locations
DNS.DiscoverNameServers()

# Ensure name servers were found or set
if not DNS.defaults.get('server'):
    print("Warning: No DNS name servers discovered. Queries might fail.")
    print("Attempting to use public DNS servers as fallback.")
    DNS.defaults['server'] = ['8.8.8.8', '8.8.4.4'] # Fallback to Google DNS

# Make an A record query for google.com
try:
    req = DNS.Request(name='google.com', qtype='A')
    response = req.req()

    print(f"DNS Query for google.com (A records):\n")
    if response.answers:
        for answer in response.answers:
            print(f"  Name: {answer.name}, Type: {answer.qtype}, Data: {answer.data}, TTL: {answer.ttl}")
    else:
        print("  No A records found for google.com.")

    # Example: MX record query
    req_mx = DNS.Request(name='example.com', qtype='MX')
    response_mx = req_mx.req()
    print(f"\nDNS Query for example.com (MX records):\n")
    if response_mx.answers:
        for answer in response_mx.answers:
            print(f"  Name: {answer.name}, Type: {answer.qtype}, Priority: {answer.data[0]}, Exchange: {answer.data[1]}")
    else:
        print("  No MX records found for example.com.")

except DNS.DNSError as e:
    print(f"DNS Error: {e}")
except Exception as e:
    print(f"An unexpected error occurred: {e}")

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