How to get an IP address from a hostname in Python

Resolving a hostname to an IP address lets a script confirm the address returned by the local resolver before it connects, logs a target, or hands the address to another network check.

The socket module passes hostname lookups to the operating system resolver. socket.gethostbyname() returns one IPv4 address string, while socket.gethostbyname_ex() returns the primary hostname, alias list, and all IPv4 addresses returned for the same name in that lookup.

Resolver results follow local DNS answers, search domains, hosts-file entries, and address rotation, so the same hostname can return different addresses across systems or between runs. Python documentation describes both functions as IPv4-only interfaces; use socket.getaddrinfo() instead when the program must handle IPv6 or select an address family explicitly.

1. Start the Python 3 interpreter.

   $ python3
   Python 3.14.4
   >>>

2. Import the socket module.

   >>> import socket

3. Resolve one hostname to one IPv4 address with socket.gethostbyname().

   >>> socket.gethostbyname("example.com")
   '172.66.147.243'

   A hostname can be a short local name or a fully qualified domain name such as example.com.

   The returned IPv4 address can differ between runs when DNS rotates across several records.

4. Resolve all IPv4 answers returned for the hostname with socket.gethostbyname_ex().

   >>> socket.gethostbyname_ex("example.com")
   ('example.com', [], ['172.66.147.243', '104.20.23.154'])

   The returned tuple is (hostname, aliaslist, ipaddrlist).

   Use socket.getaddrinfo() instead when the program needs IPv6 results or explicit address-family selection.

5. Create a short script that reads one hostname argument and prints the resolved IPv4 addresses.

   hostname-to-ip.py

   #!/usr/bin/env python3
    
   import socket
   import sys
    
   if len(sys.argv) != 2:
       raise SystemExit(f"Usage: {sys.argv[0]} <hostname>")
    
   hostname = sys.argv[1]
    
   try:
       primary_name, aliases, addresses = socket.gethostbyname_ex(hostname)
   except socket.gaierror as exc:
       raise SystemExit(f"Lookup failed for {hostname}: {exc}")
    
   print(f"Input hostname: {hostname}")
   print(f"Canonical hostname: {primary_name}")
    
   if aliases:
       print("Aliases:")
       for alias in aliases:
           print(f"  {alias}")
    
   print("IPv4 addresses:")
   for address in addresses:
       print(f"  {address}")

   The script uses socket.gethostbyname_ex() so one lookup can expose the primary name and every current IPv4 answer.

6. Run the script with a hostname and confirm that it prints the current IPv4 answers.

   $ python3 hostname-to-ip.py example.com
   Input hostname: example.com
   Canonical hostname: example.com
   IPv4 addresses:
     172.66.147.243
     104.20.23.154

   Address order and membership can change when the hostname is served through multiple records or a CDN.

7. Run the script with a reserved invalid host name to confirm the failure path.

   $ python3 hostname-to-ip.py no-such-hostname.invalid
   Lookup failed for no-such-hostname.invalid: [Errno -2] Name or service not known

   The exact resolver error text can vary by operating system, but socket.gaierror remains the failure condition to catch.