What is 255.255 255.0 subnet value?

The subnet mask is the most basic network addressing scheme that can be used for IP. The bits in a subnet mask are ones and zeros (a.a binary) representing whether a packet from a host on a network segment is allowed to enter the destination network segment or not.

In common use, it is assumed that the 255.0 subnet mask represents a network with subnets with different numbers of hosts in each, so that 255.0 is a 255.0/8 net, 255.128 is a 255.0/8 net, and 255.192 is a 255.

That being said, these represent an example of what would be considered an inclusive subnet, where all addresses from 0-254 on the subnet would be part of the subnet. In this case, you would have multiple hosts on different subnets, but no routers between them.

A more exclusive example would be 255.0/8, representing a subnet where every single address from 0-254 is on the subnet. In this case, there is no other network available on the subnet except for the hosts themselves, which is known as a private subnet.

0 subnet is called a Subnet Mask. The number 255 is the length of the network defined by the subnet mask. This means that the subnet contains 254 hosts and one router. One common use of 255.0 is a "classful" network where the class has a subnet mask of 255.

What is the easiest way to calculate subnet mask?

I know that you can do it with a calculator but the most efficient way to learn it? Using your given CIDR 10.168.1/32'
You can see this by the '/8' bit followed by '192. Note that this matches the cidr statement used in the question: cidr = '10.0/8' and you also don't need to use /32 as that is implied for a /32 CIDR by doing '/'. Also if the network you are working on doesn't fit in easily into a CIDR statement, you can instead make a network mask (like 0xF8) and do: cidr = str(CIDR). Network = '0xF8'. Netmask = cidr.replace(network, network).replace('. However I think user206504 is correct in that you may wish to use a variable cidr (in my example I've been assuming for simplicity that there will be always be an octet in the CIDR value and so there's no need for multiple octets), so you could get something like:
CidrStatement = '10.0', '192.