Python - Pandas:将列中的数字提取到新列中

Question

我一直在用python中的熊猫来提取信息。我在数据帧的一列中有以下标题：

   0
In & Out (1997)
Simple Plan, A (1998)
Retro Puppetmaster (1999)
Paralyzing Fear: The Story of Polio in America, A (1998)
Old Man and the Sea, The (1958)
Body Shots (1999)
Coogan's Bluff (1968)
Seven Samurai (The Magnificent Seven) (Shichinin no samurai) (1954)
Search for One-eye Jimmy, The (1996)
Funhouse, The (1981)

我想把这些标题的年份放在一个新的专栏中。我遇到的问题是，如果我在"("作为分隔符上进行拆分，正如您在第 8 行中看到的那样，它会在那里拆分。那么我如何在 (yyyy( 处拆分以形成一个新列，该年份看起来像这样？

     0                 1
In & Out              1997
Simple Plan, A        1998
Retro Puppetmaster    1999 
Paralyzing Fear:...   1998
Old Man and the S...  1958
Body Shots            1999
Coogan's Bluff        1968 
Seven Samurai (T...   1954
Search for One-ey...  1996
Funhouse, The         1981

Answer 1

您可以使用 expand：

df['year'] = df.iloc[:,0].str.extract('((d{4}))'',expand=False)
df
Out[381]: 
                                                   0  year
0                                    In & Out (1997)  1997
1                              Simple Plan, A (1998)  1998
2                          Retro Puppetmaster (1999)  1999
3  Paralyzing Fear: The Story of Polio in America...  1998
4                    Old Man and the Sea, The (1958)  1958
5                                  Body Shots (1999)  1999
6                              Coogan's Bluff (1968)  1968
7  Seven Samurai (The Magnificent Seven) (Shichin...  1954
8               Search for One-eye Jimmy, The (1996)  1996
9                               Funhouse, The (1981)  1981

Answer 2

您可以尝试字符串切片操作。字符串数据类型的 rindex(( 方法返回匹配模式的索引值(在本例中为从右端角开始的 '('(。使用索引值，我们可以按预期执行字符串切片。

例如：

>>> a = "Seven Samurai (The Magnificent Seven) (Shichinin no samurai) (1954)"
>>>
>>> print a[:a.rindex('(')], a[a.rindex('(')+1:-1]
Seven Samurai (The Magnificent Seven) (Shichinin no samurai)  1954    
>>>
>>>