如何使用正则表达式从字符串中提取前两个字符

reference: Pandas DataFrame: remove unwanted parts from strings in a column

参考:Pandas DataFrame:从列中的字符串中删除不需要的部分

In reference to an answer provided in the link above. I've researched some regular expressions and I plan to dive deeper but in the meantime I could use some help.

参考上面链接中提供的答案。我已经研究了一些正则表达式,我打算深入研究,但与此同时我可以使用一些帮助。

My dataframe is something like:

我的数据框是这样的:

df:

  c_contofficeID
0           0109
1           0109
2           3434
3         123434  
4         1255N9
5           0109
6         123434
7           55N9
8           5599
9           0109

Psuedo Code

If the first two characters are a 12 remove them. Or alternatively, add a 12 to the characters that don't have a 12 in the first two characters.

如果前两个字符是12则删除它们。或者,在前两个字符中没有12的字符中添加12。

Result would look like:

结果如下:

  c_contofficeID
0           0109
1           0109
2           3434
3           3434  
4           55N9
5           0109
6           3434
7           55N9
8           5599
9           0109

I'm using the answer from the link above as a starting point:

我正在使用上面链接中的答案作为起点:

df['contofficeID'].replace(regex=True,inplace=True,to_replace=r'\D',value=r'')

I've tried the following:

我尝试过以下方法:

Attempt 1)

df['contofficeID'].replace(regex=True,inplace=True,to_replace=r'[1][2]',value=r'')

Attempt 2)

df['contofficeID'].replace(regex=True,inplace=True,to_replace=r'$[1][2]',value=r'')

Attempt 3)

df['contofficeID'].replace(regex=True,inplace=True,to_replace=r'?[1]?[2]',value=r'')

1 个解决方案

#1

new answers
per comment from @Addison

来自@Addison的每条评论的新答案

# '12(?=.{4}$)' makes sure we have a 12 followed by exactly 4 something elses
df.c_contofficeID.str.replace('^12(?=.{4}$)', '')

If ID's must have four characters, it's simpler to

如果ID必须有四个字符,那么它就更简单了

df.c_contofficeID.str[-4:]

old answer
use str.replace

旧答案使用str.replace

df.c_contofficeID.str.replace('^12', '').to_frame()

#1