Question

我一直试图弄清楚这一点。我是Python的新手。

我有一张约有50,000条记录的表格。但是下表将解释我想要做的事情。

我想添加名为Category的第三列。此列将包含基于“电影”列中设置的条件的基于值的结果。

-----------------------------------------
N     | Movies               
-----------------------------------------
1        | Save the Last Dance 
-----------------------------------------
2        | Love and Other Drugs
---------------------------------------
3        | Dance with Me      
---------------------------------------
4        | Love Actually       
---------------------------------------
5        | High School Musical
----------------------------------------

条件是这样的;在“电影”栏中搜索这些单词{Dance，Love，and Musical）。如果在字符串中找到该单词，则返回“类别”列中的单词。

这将在最后产生这样的新数据帧;

-----------------------------------------
N        | Movies               | Category
-----------------------------------------
1        | Save the Last Dance  | Dance
-----------------------------------------
2        | Love and Other Drugs | Love
---------------------------------------
3        | Dance with Me        | Dance
---------------------------------------
4        | Love Actually        | Love
---------------------------------------
5        | High School Musical  | Musical
----------------------------------------

提前致谢!!

Answer 1

如果你有一个2D列表，那么就这样做：

def add_category(record):
    movie = record[1]
    categories = []
    for category in ['Dance', 'Love', 'Musical']:
        if category in movie:
            categories.append(category)
    return record.append(', '.join(categories))

database = [add_category(record) for record in database]

您可以通过更改add_category()功能来更改类别列的值的方式。

Answer 2

更快的方法是为所有类别创建一个掩码，假设您的数字很小：

In [22]:

dance_mask = df['Movies'].str.contains('Dance')
love_mask = df['Movies'].str.contains('Love')
musical_mask = df['Movies'].str.contains('Musical')
df[dance_mask]
Out[22]:
   N               Movies
0  1  Save the Last Dance
2  3        Dance with Me

[2 rows x 2 columns]

In [26]:
# now set category
df.ix[dance_mask,'Category'] = 'Dance'
df
Out[26]:
   N                Movies Category
0  1   Save the Last Dance    Dance
1  2  Love and Other Drugs      NaN
2  3         Dance with Me    Dance
3  4         Love Actually      NaN
4  5   High School Musical      NaN

[5 rows x 3 columns]

In [28]:
# repeat for remaining masks
df.ix[love_mask,'Category'] = 'Love'
df.ix[musical_mask,'Category'] = 'Musical'
df
Out[28]:
   N                Movies Category
0  1   Save the Last Dance    Dance
1  2  Love and Other Drugs     Love
2  3         Dance with Me    Dance
3  4         Love Actually     Love
4  5   High School Musical  Musical

[5 rows x 3 columns]

如何在Python中添加具有来自另一列的选定值的新列

2 个答案: