if len(dilist)>0:
dilist_one=dilist[0]
outdf=pd.merge(outdf, dilist_one, on='equ_id',how='left')

if len(dilist)>1:
    dilist = dilist[1::]
    for x in dilist:
        outdf=pd.merge(outdf, x, on=['equ_id','start_time'],how='left')

如果是第一次循环 只根据equ_id 进行合并 后期的循环是start_time和equ_id 两个字段进行合并