[英]Creating a new data frame column, by splitting a string in another column in pandas
[英]Creating a new column in Pandas DataFrame by splitting another column twice
我有以下DataFrame:
NAME
0 this_is_a_sample_2017-09-08.csv
1 this_is_a_sample_2017-09-09.csv
2 this_is_a_sample_2017-09-10.csv
3 this_is_a_sample_2017-09-11.csv
4 this_is_a_sample_2017-09-12.csv
5 this_is_a_sample_2017-09-13.csv
这是创建它的代码:
rows = ['this_is_a_sample_2017-09-08','this_is_a_sample_2017-09-09','this_is_a_sample_2017-09-10','this_is_a_sample_2017-09-11','this_is_a_sample_2017-09-12','this_is_a_sample_2017-09-13']
df = pd.DataFrame(rows, columns = ['NAME'])
我想要一个新列,其中只包含名称的日期部分。 结果数据框架如下所示:
NAME DATE
0 this_is_a_sample_2017-09-08.csv 2017-09-08
1 this_is_a_sample_2017-09-09.csv 2017-09-09
2 this_is_a_sample_2017-09-10.csv 2017-09-10
3 this_is_a_sample_2017-09-11.csv 2017-09-11
4 this_is_a_sample_2017-09-12.csv 2017-09-12
我尝试了以下方法:
df['DATE'] = df.NAME.str.split(".")[0].split('_')[-1]
我以为我可以将列拆分两次并从列表中获取日期,但是当我使用[0]
对其进行索引时,它将选择第一行(即列表)中的值。
使用.str访问器选择系列的索引,即
df['Date'] = df['NAME'].str.split(".").str[0].str.split('_').str[-1]
NAME Date 0 this_is_a_sample_2017-09-08 2017-09-08 1 this_is_a_sample_2017-09-09 2017-09-09 2 this_is_a_sample_2017-09-10 2017-09-10 3 this_is_a_sample_2017-09-11 2017-09-11 4 this_is_a_sample_2017-09-12 2017-09-12 5 this_is_a_sample_2017-09-13 2017-09-13
或使用正则表达式
df['Date'] = df['NAME'].str.extract('.*?_(\d+-\d+-\d+).csv', expand = False)
NAME Date
0 this_is_a_sample_2017-09-08.csv 2017-09-08
1 this_is_a_sample_2017-09-09.csv 2017-09-09
2 this_is_a_sample_2017-09-10.csv 2017-09-10
3 this_is_a_sample_2017-09-11.csv 2017-09-11
4 this_is_a_sample_2017-09-12.csv 2017-09-12
5 this_is_a_sample_2017-09-13.csv 2017-09-13
或按照@Evan的建议使用
df['Date'] = df['NAME'].str.extract('([\d-]+)', expand = False)
不太确定为什么要使用“ split('。')”,您真正需要的就是:
df['DATE'] = df['NAME'].str.split('_').str[-1]
NAME DATE
0 this_is_a_sample_2017-09-08 2017-09-08
1 this_is_a_sample_2017-09-09 2017-09-09
2 this_is_a_sample_2017-09-10 2017-09-10
3 this_is_a_sample_2017-09-11 2017-09-11
4 this_is_a_sample_2017-09-12 2017-09-12
5 this_is_a_sample_2017-09-13 2017-09-13
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