如何构建熊猫数据帧中项目的频率计数表?

假设我在csv文件中有以下数据, example.csv :

Word    Score
Dog     1
Bird    2
Cat     3
Dog     2
Dog     3
Dog     1
Bird    3
Cat     1
Bird    1
Cat     3

我想计算每个单词的频率。预期输出如下:

        1   2   3
Dog     2   1   1
Bird    0   1   1
Cat     1   0   2

我的代码如下:

将熊猫作为PD导入

x1 = pd.read_csv(r'path\to\example.csv')

def getUniqueWords(allWords) :
    uniqueWords = [] 
    for i in allWords:
        if not i in uniqueWords:
            uniqueWords.append(i)
    return uniqueWords

unique_words = getUniqueWords(x1['Word'])
unique_scores = getUniqueWords(x1['Score'])

scores_matrix = [[0 for x in range(len(unique_words))] for x in range(len(unique_scores)+1)]   
# The '+1' is because Python indexing starts from 0; so if a score of 0 is present in the data, the 0 index will be used for that. 

for i in range(len(unique_words)):
    temp = x1[x1['Word']==unique_words[i]]
    for j, word in temp.iterrows():
        scores_matrix[i][j] += 1  # Supposed to store the count for word i with score j

但这会产生以下错误:

IndexError                                Traceback (most recent call last)
<ipython-input-123-141ab9cd7847> in <module>()
     19     temp = x1[x1['Word']==unique_words[i]]
     20     for j, word in temp.iterrows():
---> 21         scores_matrix[i][j] += 1

IndexError: list index out of range

而且,即使我可以修复这个错误, scores_matrix 不显示标题( Dog , Bird , Cat 作为行索引,以及 1 , 2 , 3 作为列索引)。我希望能够访问每个单词的计数和每个分数-达到这种效果:

scores_matrix['Dog'][1]
>>> 2

scores_matrix['Cat'][2]
>>> 0

那么,我如何解决/解决这两个问题呢?