def delete_col(a, colnumber):
    """
    Return the matrix a without row colnumber
    If colnumber is not correct (between 0 et len(a[0])-1) the function return the a matrix without modification
    :param a: a 2 dimensional array
    :param colnumber: an int between 0 et len(a[0])-1
    :return: a 2 dimensional array
    """
    return [[a[i][j] for j in range(len(a[i])) if j != colnumber] for i in range(len(a))]