Need a structure with multiple members

[Thomas Gagne]

The struct module is interesting for creating a string encoded with binary
data, but the pack() and unpack() functions don't seem to describe how once
created you would safely access members of that structure.

For instance, I want to create a class that mirrors the C header:

typedef struct {
    int32_t len;
    int32_t sequence;
    int16_t reply;
    int16_t error;
    /* blah blah blah for 64 bytes total */
} isdHeader;

It as though I coudl start my isdHeader class as:

class IsdHeader:
    def __init__(self):
        self.data = struct.pack('llhh', 0, 0, 0, 0)

But I would like to create member functions (methods) for accessing the
various members, such that:

h = IsdHeader();
h.len(20) // sets h.len to 20
h.len()   // returns the value of h.len (the member)

I'm kinda of reading, "Quick Python" and trying to code the interface library
at the same time, and I haven't read everything yet...