def get_nr_dic1_keys_in_dic2(dic1, dic2):
    """
    Return number of dic1 keys found in dic2.

    >>> d1 = {'hallo': 1, 'hello' : 1}
    >>> d2 = {'hallo': 1, 'hello' : 1, "bonjour" : 1}
    >>> get_nr_dic1_keys_in_dic2(d1, d2)
    2
    >>> d1 = {'hollo': 1, 'ciao' : 1}
    >>> get_nr_dic1_keys_in_dic2(d1, d2)
    0

    """
    assert dic1, "dic1 empty"
    assert dic2, "dic2 empty"
    dic1_keys_found = 0
    for key in dic1:
        if key in dic2:
            dic1_keys_found += 1
    return dic1_keys_found