请问id相同的行超过50行，如果缩减为25行？

Question

请问id相同的行超过50行，如果缩减为25行？python想用 if item["New_ID"] %2==0 的方式取奇数或者偶数，请问应该怎么写呀

newDf1 = pd.DataFrame(columns=['Time', 'eleCur',  'id'])
for key, item in df1.groupby(['id']):
    if item.shape[0] > 20 :
        if item["New_ID"] %2==0:
            item['id'] = key
            newDf1 = pd.concat([newDf1, item])
            print(key)
            print(item)

Answer 1

newDf1.insert(0, 'New_ID', range(1, 1 + len(newDf1)))
newDf2= pd.DataFrame(columns=['Time', 'eleCur', 'id'])
for key, item in newDf1.groupby(['id']):

item['id'] = key
if item.shape[0] > 4000:
    item = item[item["New_ID"] % 20 == 0]
elif item.shape[0] > 3000 :
    item = item[item["New_ID"] % 15 == 0]
elif item.shape[0] > 2500:
    item = item[item["New_ID"] % 12 == 0]
elif item.shape[0] > 2000 :
    item = item[item["New_ID"] % 10 == 0]
elif item.shape[0] > 1000 :
    item = item[item["New_ID"] % 8 == 0]
elif item.shape[0] > 500:
    item = item[item["New_ID"] % 5 == 0]
elif item.shape[0] > 50 :
    item = item[item["New_ID"] % 2 == 0]
else:
    item = item
newDf2 = pd.concat([newDf2, item])