Mailman 3 Add __len__ to ipaddress._BaseNetwork - Python-ideas

26 Oct 2021


      Currently, ipaddress._BaseNetwork (and by extension, ipaddress.IPv4Network and ipaddress.IPv6Network) does not have a __len__ method, it only has num_addresses.
This makes the following code not work:
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...
...
random.choice(ipaddress.ip_network('6.0.0.0/8'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/nyuszika7h/.pyenv/versions/3.10.0/lib/python3.10/random.py", line 378, in choice
    return seq[self._randbelow(len(seq))]
TypeError: object of type 'IPv4Network' has no len()
The workaround is a bit ugly:
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(network := ipaddress.ip_network('6.0.0.0/8'))[random.randrange(network.num_addresses)]
IPv4Address('6.60.184.142')
With a custom subclass, all works well:
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class MyIPv4Network(ipaddress.IPv4Network):
...     def __len__(self):
...         return self.num_addresses
...
...
...
...
random.choice(MyIPv4Network('6.0.0.0/8'))
IPv4Address('6.40.110.63')