def isnull(x, row = 1, keep = None, col = 0):
    if row!=1 or col!=0: axis = 0
    else: axis = 1
    if keep is None: miss = missing(x, row = axis)!=0
    else:
        if axis == 1:
            if keep < 1: miss = missing(x, row = axis)<=shape(x)[1]*keep
            else: miss = missing(x, row = axis)<=keep
        else:
            if keep < 1: miss = missing(x, row = axis)<=len(x)*keep
            else: miss = missing(x, row = axis)<=keep
    try: return x.iloc[miss.index[miss]]
    except: return x[pd.isnull(x)==True]