Random "programming language"

Question

I decided to write my own programming language, of sorts. Essentially, you write code into a text file and the program will run the code inside the text file. The file is provided through a script argument.

# Basic programming language
from operator import eq, ne, lt, gt, le, ge
from random import random
from sys import exit, argv
# Specify file to be run
code = argv([1])
"""
>> - Specify to the user that something will be outputted.
<< - Specify to the user that something will be inputted.
"""
# Dict storing operators
OPERATORS = {
 "==": eq,
 "!=": ne,
 "<=": le,
 ">=": ge,
 "<": lt,
 ">": gt
}
# Dict storing program data
data = {
 "vars": [0] * 100000,
 "rand": random()
}
# Interpret the code
def interpreter(separator):
 for line in open(code, "r").readlines():
 # Split each line
 s_command = line.split(separator)
 # Basic input and output
 if s_command[0] == "$out" and s_command[1] == ">>":
 if s_command[2] in data:
 print data[s_command[2]]
 if s_command[2] not in data:
 print s_command[2]
 if s_command[0] == "$inp" and s_command[1] == "<<":
 inp = raw_input(s_command[2])
 # Assign integer variables
 if s_command[0] == "$assignint" and s_command[1] == "<<":
 data["vars"][int(s_command[2])] = int(s_command[3])
 # Assign string variables
 if s_command[0] == "$assignstr" and s_command[1] == "<<":
 data["vars"][int(s_command[2])] = s_command[3]
 # Return variable values
 if s_command[0] == "$return" and s_command[1] == ">>":
 print data["vars"][int(s_command[2])]
 # Test integer values
 if s_command[0] == "$testint" and s_command[1] == ">>":
 if s_command[3] in OPERATORS:
 print OPERATORS[s_command[3]](
 int(s_command[2]),
 int(s_command[4]))
 # Test string values
 if s_command[0] == "$teststr" and s_command[1] == ">>":
 if s_command[3] in OPERATORS:
 print OPERATORS[s_command[3]](
 s_command[2],
 s_command[4])
 # Test variable values
 if s_command[0] == "$testvar" and s_command[1] == ">>":
 if s_command[3] in OPERATORS:
 print OPERATORS[s_command[3]](
 data["vars"][int(s_command[2])],
 data["vars"][int(s_command[4])])
 # Terminate the program
 if s_command[0] == "$exit" and s_command[1] == ">>":
 exit(int(s_command[2]))
# Run the interpreter
if __name__ == "__main__":
 while True:
 interpreter(":")

Here's an example of a code file:

$out:>>:Hello world.
$inp:<<:[input]>
$assignint:<<:0:10
$assignint:<<:1:11
$return:>>:0
$return:>>:1
$testvar:>>:0:==:1
$testvar:>>:0:!=:1
$exit:>>:0

All I'm really looking for is a way to turn that ugly if/else chain into something prettier without changing the original syntax.

Answer 1

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 = {
 ("$out", ">>"): do_out,
 ("$inp", "<<"): do_inp,
 ("$assignint", "<<"): 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)