Python pandas nunique() 数据类型

Question

我有一个简单的 pandas DataFrame，我们称它为 ratings:

ratings = pd.read_csv("ratings.csv", header=0, delimiter=",")
print(ratings)

userId  movieId  rating
    1        1     4.0
    1        3     4.5
    2        6     4.0
    3        2     5.5
    3       11     3.5
    3       32     3.0
    4        4     4.0
    5       26     4.5

我正在尝试获取列的不同值的数量，我发现 :

Count distinct values, use nunique:
df['hID'].nunique()
Count only non-null values, use count:
df['hID'].count()
Count total values including null values, use the size attribute:
df['hID'].size

所以我关注了：

print("%s unique users" % ratings["userId"].nunique())

并得到这样的输出：

(5,) unique users

阅读pandas.DataFrame.nunique()文档后，我检查了它的数据类型：

print(type(ratings["userId"].nunique()))

<class 'tuple'>

现在我不知道如何在另一个变量中将此值用作数值。如果我把它包在里面 int():

print(type(int(ratings["userId"].nunique())))

输出仍将是 <class 'tuple'>，从另一个代码调用该变量将引发错误。

我对 Python 很陌生，所以我可能会提出愚蠢的问题。感谢阅读并帮助我解决这个问题！

编辑：这是我的真实代码（因为它不支持用于注释的正确代码格式）：

ratings = pd.read_csv(
    "../ml-latest-small/ratings.csv",
    header=0,
    delimiter=",",
    usecols=["userId", "movieId", "rating"]
)

numof_movies = ratings["movieId"].nunique()[0],
numof_users = ratings["userId"].nunique(),
numof_ratings = len(ratings)

print("\n%s movies, %s users and %s ratings are given\n" % (
    numof_movies,
    numof_users,
    type(numof_ratings)
))

以及 ratings.csv 文件的样子：

userId,movieId,rating,timestamp
1,1,4.0,964982703
1,3,4.0,964981247
1,6,4.0,964982224
1,47,5.0,964983815
1,50,5.0,964982931
...

以及当我将它打印到终端时 DataFrame 的外观：

        userId  movieId  rating
0            1        1     4.0
1            1        3     4.0
2            1        6     4.0
3            1       47     5.0
4            1       50     5.0
...        ...      ...     ...
100831     610   166534     4.0
100832     610   168248     5.0
100833     610   168250     5.0
100834     610   168252     5.0
100835     610   170875     3.0

Answer 1

unique_users = ratings["userId"].nunique()
print(f"{unique_users} unique users" )

Answer 2

IIUC：

import pandas as pd
from io import StringIO

rating_txt = StringIO("""userId,movieId,rating,timestamp
1,1,4.0,964982703
1,3,4.0,964981247
1,6,4.0,964982224
1,47,5.0,964983815
1,50,5.0,964982931""")

ratings_df = pd.read_csv(rating_txt)
ratings_df

print(f"{ratings_df['movieId'].nunique()} movies, {ratings_df['userId'].nunique()} user(s), and {ratings_df['rating'].count()} ratings are given.")

输出：

5 movies, 1 user(s), and 5 ratings are given.

Python pandas nunique() 数据类型

Python pandas nunique() datatype

python

count

unique-values

dataframe

pandas