SublimeREPL returning unhelpful error, functional in IDLE

Question

I'm using Sublime Text 2, Package Control, and SublimeREPL to (try) to create and run python code. The code, a simple Brainfuck interpreter, is as follows. However this isn't the problem:

import sys

def brainfuck(arg_bf_string):

    bf_string = arg_bf_string
    bf_string_pointer = 0

    value_array = [0] * 65536
    value_array_pointer = 0

    running = True
    while running:

        if bf_string[bf_string_pointer] == ">":
            value_array_pointer += 1

        if bf_string[bf_string_pointer] == "<":
            value_array_pointer -= 1

        if bf_string[bf_string_pointer] == "+":
            value_array[value_array_pointer] += 1

        if bf_string[bf_string_pointer] == "-":
            value_array[value_array_pointer] -= 1

        if bf_string[bf_string_pointer] == ".":
            sys.stdout.write(chr(value_array[value_array_pointer]))

        if bf_string[bf_string_pointer] == ",":
            value_array[value_array_pointer] = ord(raw_input("INP "))

        if bf_string[bf_string_pointer] == "[":
            if value_array[value_array_pointer] == 0:

                loop_depth = 0
                loop_pointer = bf_string_pointer + 1
                loop_searching = True

                while loop_searching:
                    if bf_string[loop_pointer] == "[":
                        loop_depth += 1

                    elif bf_string[loop_pointer] == "]" and loop_depth > 0:
                        loop_depth -= 1

                    elif bf_string[loop_pointer] == "]" and loop_depth == 0:
                        bf_string_pointer = loop_pointer
                        loop_searching = False

                    loop_pointer += 1

        if bf_string[bf_string_pointer] == "]":
            if value_array[value_array_pointer] != 0:

                loop_depth = 0
                loop_pointer = bf_string_pointer - 1
                loop_searching = True

                while loop_searching:
                    if bf_string[loop_pointer] == "]":
                        loop_depth += 1

                    elif bf_string[loop_pointer] == "[" and loop_depth > 0:
                        loop_depth -= 1

                    elif bf_string[loop_pointer] == "[" and loop_depth == 0:
                        bf_string_pointer = loop_pointer
                        loop_searching = False

                    loop_pointer -= 1

        bf_string_pointer += 1
        if bf_string_pointer > len(bf_string)-1:
            running = False

def main():
    brainfuck(raw_input("BF "))

I successfully ran this code in IDLE without a hitch, so I'm certain the code itself isn't an issue.

When using SublimeREPL to run it however, I get the following error:

>>> Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1
    Python 2.7.6 (default, Nov 10 2013, 19:24:18) [MSC v.1500 32 bit (Intel)] on win32
             ^

And I have no idea where that's coming from. I can replicate this by simply loading the file into Sublime Text, and selecting Tools > SublimeREPL > Eval in REPL > File.

I've tried Tools > SublimeREPL > Python > Python - RUN Current File as well. When doing this, I receive the following in a REPL tab:

C:\Python27\python.EXE: can't open file '$file_basename': [Errno 2] No such file or directory

***Repl Closed***

I can type in the prompt, but it's completely unresponsive. I guessed it was something wrong with my Python installation. I'm not sure what to do about it or how to fix it, or if it's something I should even be worried about.

As far as I know I've installed SublimeREPL properly, using Package Control and copying the SublimeREPL settings from Settings - Default to Settings - User. I've tried reinstalling my Python installation. Any help is appreciated.

Answer 1

You are missing something critical in your program - a way to run it. Traditionally, that consists of the following at the end of the file:

if __name__ == '__main__':
    main()

Unlike C programs, for example, just defining a main() function doesn't automatically mean it'll be executed when the file is run - it needs to be called explicitly.

Once I added those lines to the program, I was able to execute the following Hello World program (from Wikipedia):

++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.

by running Tools -> SublimeREPL -> Python -> Python - RUN Current File. If you want to interact with the program a little more, first make sure you have a Python REPL open, then select Tools -> SublimeREPL -> Eval in REPL -> File. This will load the brainfuck() and main() functions in memory, so you can run them more than once if you wish.