Written by
akendo

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# Converting a netmask to CIDR with vanilla python

On a quick note:

I wasn’t able to find a simple solution to convert a classicly formated netmask to a CIDR format in python. So I wrote this line:

```
sum([ bin(int(bits)).count("1") for bits in m_netmask.split(".") ])
```

Place into a function:

```
def netmask_to_cidr(m_netmask):
return(sum([ bin(int(bits)).count("1") for bits in m_netmask.split(".") ]))
```

It takes a netmask as a string (for example `255.255.255.0`

) and will convert it into a binary representation, then it will count the ones in it.
Subsequently it computes the sum of the count result. Very simple.

Some examples:

```
In [79]: netmask_to_cidr('255.255.255.0')
Out[79]: 24
In [80]:
In [80]: netmask_to_cidr('255.255.255.255')
Out[80]: 32
In [81]: netmask_to_cidr('255.255.255.128')
Out[81]: 25
```

Please be aware it assume you have a valid netmask as input.

You can also see it here

have fun!