using C struct with u8, u16 in Python dictionary

Question

So I have a C struct like this below

struct spi_header
{
    u8  SpiCmd  :5;
    u8  channel :1;
    u8  kac     :2;
};

which I need to use in python, so I tried using dictionary for this, as shown below

 spi_header = { 'SpiCmd': , 'channel': , 'kac': }

I tried assigning range for the members like 'SpiCmd' : (0:5) trying to split the bytes into the range specified in the C structure. But I get syntax error. I know it is, because the range can't be specified (5, 1, 2) like how I tried. So how do I write in python, can any help me with this?