pybf.py

def interpret(source):
    op = [0] * 255
    pointer = 0
    i = 0
    start = []
    while i < len(source):
        if source[i] == '<':
            pointer -= 1
        elif source[i] == '>':
            pointer += 1
        elif source[i] == '+':
            op[pointer] += 1
        elif source[i] == '-':
            op[pointer] -= 1
        elif source[i] == '.':
            sys.stdout.write(chr(op[pointer]))
        elif source[i] == ',':
            char = raw_input()
            while len(char) != 1:   # 一次只读入一个字节
                char = raw_input()
            op[pointer] = ord(char)
        elif source[i] == '[':
            start.append(i) # 存储循环开始的位置
            shellCount = len(start) # 目前的循环层数
            # 寻找对应的循环结束符
            for j in range(len(source) - 1, i + 1, -1):
                if source[j] == ']':
                    shellCount -= 1
                if shellCount == 0:
                    i = j - 1   # 跳转至对应的循环结束符
                    break
        else:
            if op[pointer] != 0:
                i = start[-1]   # 返回对应的循环开始符的下一指令
            else:
                del start[-1]   # 删除栈顶的循环开始符记录
        i += 1