def all_digits(los):
    """Return a boolean value indicating if all the strings in the given list of
    strings contain at least one digit and nothing but digits.

    >>> all_digits(['1', '', '234'])
    False
    >>> all_digits(['1234', '321'])
    True
    >>> all_digits(['1.2'])
    False
    >>>
    """
    #.
    #.
    #.
    #.

def all_equal(lst):
    """Return a boolean indicating if all the values in the given list are
    equal (which is trivially true if the list is empty).

    >>> all_equal(['x', 'x', 'x'])
    True
    >>> all_equal([1])
    True
    >>> all_equal([])
    True
    >>> all_equal([1, 2])
    False
    >>>
    """
    #.
    #.
    #.
    #.
    #.
    #.

def remove_zeros(lon):
    """Return a list containing those value in the given list of numbers that
    are not zero.

    >>> remove_zeros([1, 0, -3, 0, 0, 4, 1])
    [1, -3, 4, 1]
    >>>
    """
    #.
    #.
    #.
    #.
    #.
    #.

def concatenate_tables(table1, table2):
    """Return a table whose rows are formed by concatinating corresponding rows
    of the given tables. Assume the tables have the same number of rows.

    >>> t1 = [['a'], ['b'], ['c']]
    >>> t2 = [[1, 2], [3, 4], [5, 6]]
    >>> concatenate_tables(t1, t2)
    [['a', 1, 2], ['b', 3, 4], ['c', 5, 6]]
    >>>
    """
    #.
    #.
    #.
    #.

def delete_column(table, column_index):
    """Delete from the table the indicated column and return None.

    >>> t = [['a', 1, 2], ['b', 3, 4], ['c', 5, 6]]
    >>> delete_column(t, 1)
    >>> t
    [['a', 2], ['b', 4], ['c', 6]]
    >>>
    """
    # Hint: use a del statement
    #.
    #.
    #.

def has_duplicates(lst):
    """Return a boolean value indicating if the list has any duplicate values.

    >>> has_duplicates([3, 2, 5, 2, 8])
    True
    >>> has_duplicates([3, 2, 5, 9, 8])
    False
    >>>
    """
    # Hint: for best efficiency, see if two consecutive values in a sorted copy
    # of the list are the same.
    #.
    #.
    #.
    #.
    #.
    #.