def createboard(rows,columns):
    """ Creates a string given rows and columns desired
        that can be converted into a matrix through numpy

    >>> createboard(5,4)
    '0,0,0,0,0; 0,0,0,0,0; 0,0,0,0,0; 0,0,0,0,0'
    >>> createboard(3,7)
    '0,0,0; 0,0,0; 0,0,0; 0,0,0; 0,0,0; 0,0,0; 0,0,0'
    """
    row_size = ''
    for rows in range(rows):
        if rows == 0:
            row_size = row_size + '0'
        else:
            row_size = row_size + ',0'
    fullmatrix = ''
    for cols in range(columns):
        if cols == 0:
            fullmatrix = fullmatrix + row_size
        else:
            fullmatrix = fullmatrix + '; ' + row_size
    return fullmatrix