sum of list or tuple with/without str and int

__author__ = 'vito-Z80'
def sum(totals,*args):
    """
    totals                              = list or tuple
    *args:
    [N,N], (N,N)                        = the beginning and the end of the added values (end= -1)
    [N],(N)                             = sequence of the added values from the beginning to N (-1)
    'all'                               = amount of all string and numerical values
    'str'                               = amount of all string values

    totals=1,3,5,'spam','eggs',7,10     = list or tuple
    (sum(totals)                        = only numerical
    (sum(totals,'all')                  = numerical + strings
    (sum(totals,'str')                  = only string
    (sum(totals,[2,6])                  = only numerical from 2 to 6-1
    (sum(totals,[4],'str')              = only string from 0 to 4-1
    (sum(totals,'all',[3,999])          = numerical + strings from 3 to end
    """
    result,start,end,full_sum=0,0,len(totals),False
    if type(totals)==str:return len(totals)
    for i in args:
        if type(i)==str:full_sum=i
        elif type(i)==list or tuple:
            if len(i)==2:start,end=i[0],i[1]
            else: end=i[0]
    for field in totals:
        if start == 0 and end:
            if full_sum=='str':
                if type(field)==str:result+=len(field)
            else:
                if type(field)==int:result+=field
                else:
                    if full_sum=='all':result+=len(field)
            start+=1
        end-=1
        start-=1
    return result

if __name__ == '__main__':
    totals=1,3,5,'spam','eggs',7,10
    print(sum(totals))
    print(sum(totals,'all'))
    print(sum(totals,'str'))
    print(sum(totals,[2,6]))
    print(sum(totals,[4],'str'))
    print(sum(totals,'all',[3,999]))