pandas 统计某一列中各个值的出现次数

例如：统计grammer列中每种编程语言出现的次数
data = {"grammer":["Python","C","Java","GO",np.nan,"SQL","PHP","Python"],
"score":[1,2,np.nan,4,5,6,7,10]}
frame = pd.DataFrame(data)

一开始要有：
import pandas as pd
import numpy as np

可以使用DataFrame的名字.列的名字.value_counts(),便可统计出列中各个元素出现的次数
words = frame.grammer.value_counts()
print(words)