Random "programming language"
It looks like all your tests follow the pattern

if s_command[0] == "$xxxxx" and s_command[1] == "yyyyy":


So what you can do is create a tuple of the first two elements of s_command:

instr = tuple(s_command[:2])


Then, you can do

if instr == ("$xxxxx", "yyyyy"):


Next, you can use a dictionary to collect all your instructions in one place:

Instructions = {
    ("$out", "&gt;&gt;"): do_out,
    ("$inp", "&lt;&lt;"): do_inp,
    ("$assignint", "&lt;&lt;"): do_assignint,
    ...
}


Then you would define a number of functions, one for each instruction, such as

def do_inp(s_command):
    inp = raw_input(s_command[2])


and call your methods with

Instructions[instr](s_command)