Brainfuck to Shakespeare

import sys

#Use like the following:
#   this-program.py bf-program.bf spl-program.spl
#
#Alternatively, if you don't provide the output name, or either name, the program will prompt you.

try:
    BFprogramName = sys.argv[1]
except:
    BFprogramName = input("Enter name of brainfuck program: ")

with open(BFprogramName,"r") as f:
    BFprogram = f.read()


def roman(a):
    return "".join(reversed(["".join(["IVXLCDM"[int(d)+i*2]for d in["","0","00","000","01","1","10","100","1000","02"][int(c)]])for i,c in enumerate(reversed(str(a)))]))

header = """Brainfuck.

Lennox, the number of entries in the stack.
Page, the memory pointer.
Shallow, a temporary variable that tells how deep in the stack to go.
Julius Caesar, another temporary variable.
King Henry, the "real" stack.
King John, who holds a part of the stack as necessary.

Act I: Setup of the stack and variables.

Scene I: The stack will be 24 entries long in this example; change what Julius Caesar says to extend it.

[Enter Julius Caesar and Lennox]

Julius Caesar:
Thou art the factorial of a big huge stone wall!

Lennox:
You are as huge as me.

[Exit Lennox]
[Enter King Henry]

Scene II: Producing the stack with a loop.

Julius Caesar:
Remember nothing!

King Henry:
Thou art as stupid as the sum of thyself and thy death!

Julius Caesar:
Am I as cunning as a pig? If not, we must return to Scene II.

Act II: The rest of the program.

Scene I: This scene must be here if your program doesn't start with a bracket.

"""
getStack = """[Exeunt]
[Enter Lennox and Shallow]

Lennox:
You are the difference between myself and the sum of Page and the Devil!

Scene @: Retrieve the correct number in the stack with a loop.

[Exeunt]
[Enter King Henry and King John]

King John:
Recall!

King Henry:
Remember me!

[Exit King John]
[Enter Shallow]

King Henry:
Thou art the sum of thyself and the Devil!

Shallow:
Am I as mighty as nothing? If not, we must return to Scene @.

"""
fixStack = """[Exeunt]
[Enter Lennox and Shallow]

Lennox:
You are the difference between myself and Page!

[Exeunt]
[Enter King Henry and Julius Caesar]

King Henry:
Thou art as noble as me.

[Exit Julius Caesar]
[Enter King John]

King Henry:
Recall!

King John:
Remember thyself!

Scene #: Put the stack back together again with a loop.

[Exeunt]
[Enter King Henry and King John]

King Henry:
Recall!

King John:
Remember me!

[Exit King John]
[Enter Shallow]

King Henry:
Thou art the sum of thyself and the Devil!

Shallow:
Am I as mighty as nothing? If not, we must return to Scene #.

"""

BAK = """[Exeunt]
[Enter King Henry and Page]

King Henry:
Thou art the sum of thyself and the Devil! Art thou worse than nothing? If so, thou art as good as the sum of Lennox and the Devil.

"""
FWD = """[Exeunt]
[Enter King Henry and Page]

King Henry:
Thou art the sum of thyself and the Lord! Art thou better than the sum of Lennox and the Devil? If so, thou art nothing.

"""
INC = getStack + """Shallow:
You are the sum of yourself and a king! Are you better than the sum of a brave brave brave brave brave brave brave brave hero and a coward? If so, you are nothing.

""" + fixStack
DEC = getStack + """Shallow:
You are the sum of yourself and a plague! Are you worse than nothing? If so, you are the sum of a brave brave brave brave brave brave brave brave hero and a coward.

""" + fixStack
IN = getStack + """Shallow:
Open your mind!

""" + fixStack
OUT = getStack + """Shallow:
Speak your mind!

""" + fixStack
IF = """Scene $: If the current value is 0, skip to the matching right bracket.

""" + getStack + fixStack + """[Exeunt]
[Enter Julius Caesar]

Julius Caesar:
Am I as cunning as nothing? If so, we must proceed to scene %.

"""
EIF = """Scene $: If the current value is not 0, jump back to the matching left bracket.

""" + getStack + fixStack + """[Exeunt]
[Enter Julius Caesar]

Julius Caesar:
Am I as cunning as nothing? If not, we must return to scene %.

"""

SPLprogram = header
if BFprogram[0] == "[":
    SPLprogram += """[Exeunt]

"""

ifPositions = []
eifPositions = []
sceneCount = 1

for i in range(len(BFprogram)):
    if BFprogram[i] in "+-,.":
        sceneCount += 2
    elif BFprogram[i] == "[":
        sceneCount += 1
        ifPositions.append(sceneCount)
        sceneCount += 2
        ifCount = 1
        newSceneCount = sceneCount
        j = i + 1
        while not (j >= len(BFprogram) or ifCount == 0):
            if BFprogram[j] in "+-,.":
                newSceneCount += 2
            elif BFprogram[j] == "[":
                newSceneCount += 3
                ifCount += 1
            elif BFprogram[j] == "]":
                newSceneCount += 3
                ifCount -= 1
            j += 1
        eifPositions.append(newSceneCount-2)
    elif BFprogram[i] == "]":
        sceneCount += 3

sceneCount = 1
for i in BFprogram:
    if i == "<":
        SPLprogram += BAK
    elif i == ">":
        SPLprogram += FWD
    elif i == "+":
        SPLprogram += INC.replace("@",roman(sceneCount+1)).replace("#",roman(sceneCount+2))
        sceneCount += 2
    elif i == "-":
        SPLprogram += DEC.replace("@",roman(sceneCount+1)).replace("#",roman(sceneCount+2))
        sceneCount += 2
    elif i == ",":
        SPLprogram += IN.replace("@",roman(sceneCount+1)).replace("#",roman(sceneCount+2))
        sceneCount += 2
    elif i == ".":
        SPLprogram += OUT.replace("@",roman(sceneCount+1)).replace("#",roman(sceneCount+2))
        sceneCount += 2
    elif i == "[":
        command = IF.replace("$",roman(sceneCount+1))
        command = command.replace("@",roman(sceneCount+2))
        command = command.replace("#",roman(sceneCount+3))
        command = command.replace("%",roman(eifPositions[ifPositions.index(sceneCount+1)]))
        SPLprogram += command
        sceneCount += 3
    elif i == "]":
        command = EIF.replace("$",roman(sceneCount+1))
        command = command.replace("@",roman(sceneCount+2))
        command = command.replace("#",roman(sceneCount+3))
        command = command.replace("%",roman(ifPositions[eifPositions.index(sceneCount+1)]))
        SPLprogram += command
        sceneCount += 3

try:
    programName = sys.argv[2]
except:
    programName = input("Enter name of output program: ")

print("Writing program...")
with open(programName,"w") as f:
    f.write(SPLprogram)