使用正则表达式基于逗号字符分隔列数据

Question

我有一个如下所示的数据帧

df = pd.DataFrame({'val': ['V583 ,ATTENTION, PRIMARY','Y9207,INDOOR LIVING, sEcondary',' z526, liver,primary ','12345678, test, secondary',',project,']})

我想基于comma字符分割/隔离列val数据

例如，所有字符before 1st comma都应该转到first列 同样，所有字符after 1st comma和before 2nd comma都应该转到second列 同样，所有字符after 2nd comma和before 3rd comma都应该转到third列

我试过下面的方法

df['val'].astype(str).str.extract(r'\s*([a-zA-Z0-9\s]*)',expand=True)

我希望我的输出如下所示

Answer 1

有了您展示的样品，请尝试以下内容。在这里使用Pandas的^{}函数。简单的解释是：在extract中提到regex以在DataFrame中创建3个新列。它基本上是根据显示的示例为每个新字段创建3个捕获组

df[["first", "second", "third"]] =  df['val'].str.extract(r'^([^,]*),([^,]*),(.*)$',expand=True)

Here is online demo of above regex

df的输出如下所示：

                              val     first         second       third
0        V583 ,ATTENTION, PRIMARY     V583       ATTENTION     PRIMARY
1  Y9207,INDOOR LIVING, sEcondary     Y9207  INDOOR LIVING   sEcondary
2            z526, liver,primary       z526          liver    primary 
3       12345678, test, secondary  12345678           test   secondary
4                       ,project,                  project