Number Base bruteforce checker

from enum import Enum

class NumberBase(Enum):
    DECIMAL = 'DECIMAL'
    HEX = 'HEX'
    OCTAL = 'OCTAL'
    BINARY = 'BINARY'

def parse_number_base(str):
    curr_state = 'START'
    init_DEC_OCT_HEX = [chr(i) for i in range(49,56)]
    l_alph = [chr(i) for i in range(97,103)]
    u_alph = [chr(i) for i in range(65,71)]
    OCT = [chr(i) for i in range(48,56)]
    DEC_HEX = [chr(i) for i in range(48,58)]
    for char in str:
        if curr_state == 'START':
            if len(str) == 0:
                return None
            elif char == '0':
                curr_state = 'ZERO'
            elif char in init_DEC_OCT_HEX:
                curr_state = 'DEC_OCT_HEX'
            elif char == '8' or char == '9':
                curr_state = 'DEC_HEX'
            elif char in l_alph or char in u_alph:
                curr_state = 'HEX'
            else:
                return None
        elif curr_state == 'ZERO':
            if char == 'b' or char == 'B':
                curr_state = 'BIN_START'
            elif char in OCT:
                curr_state = 'OCT'
            elif char == 'x' or char == 'X':
                curr_state = 'HEX_START'
            else:
                return None
        elif curr_state == 'DEC_OCT_HEX':
            if char in OCT:
                curr_state = 'DEC_OCT_HEX'
            elif char in l_alph or char in u_alph:
                curr_state = 'HEX'
            elif char == '8' or char == '9':
                curr_state = 'DEC_HEX'
        elif curr_state == 'BIN_START':
            if char == '0' or char == '1':
                curr_state = 'BIN'
            else:
                return None
        elif curr_state == 'HEX_START':
            if char in DEC_HEX or char in l_alph or char in u_alph:
                curr_state = 'HEX'
            else:
                return None
        elif curr_state == 'DEC_HEX':
            if char in DEC_HEX:
                curr_state = 'DEC_HEX'
            elif char in l_alph or char in u_alph:
                curr_state = 'HEX'
            else:
                return None
        elif curr_state == 'HEX':
            if char in DEC_HEX or char in l_alph or char in u_alph:
                curr_state = 'HEX'
            else:
                return None
        elif curr_state == 'BIN':
            if char == '0' or char == '1':
                curr_state = 'BIN'
            else:
                return None
        elif curr_state == 'OCT':
            if char in OCT:
                curr_state = 'OCT'
            else:
                return None
    if curr_state == 'ZERO' or curr_state == 'DEC_OCT_HEX' or curr_state == 'DEC_HEX':
        return NumberBase.DECIMAL
    elif curr_state == 'BIN':
        return NumberBase.BINARY
    elif curr_state == 'OCT':
        return NumberBase.OCTAL
    elif curr_state == 'HEX':
        return NumberBase.HEX
    else:
        return None