def bull_engulf(Open, high, low, close, t=4):
    """
    Identifies if prices is a Bullish Engulfing Pattern of not
    
    Param:
        Open: array of open prices (5-day)
        high: array of high prices (5-day)
        low: array of low prices (5-day)
        close: array of close prices (5-day)
        t: int num. day -1 (5-1=4)
    Return:
        status: boolean true if it is the pattern
    """
    if len(Open) < 5:
        raise AttributeError('Prices are not length 5')
        
    if (Open[t] < close[t-1] and 
        close[t] > Open[t-1] and 
        Open[t] < close[t] and 
        Open[t-1] > close[t-1] and
        (Open[t-2]>close[t-2] and Open[t-3]>close[t-3] and Open[t-4]>close[t-4]) and
        (close[t-2]<close[t-3]<close[t-4])):
        return True
    
    return False