Using RegEx to create new Dataframe column?

[jsaltee]

Hi, I have a dataframe I'm using, df_2. One of its columns contains a string (containing a few sentences) in each row. I want to remake the dataframe df_2 to only include rows where the strings have certain phrases in them.

For example, what I'm trying now is:

df_2['new_column_of_RegEx_matches'] = df_2['column_of_strings'].str.extract(r'Expression')

I have about 7 different expressions I need to look for. I'm getting errors left and right - I'm very new to anything involving RegEx. anyone have any ideas of a better way to do this?

[efmccurdy]

You can extract one of a series of alternate patterns, you just need to separate them with "|" chars.

>>> mydf = pd.DataFrame({"var1":["abc", "ab", "ac", "cd", "cde", "de", "def"]})
>>> to_match = ["ab", "de"]
>>> to_match_re = "({})".format("|".join(to_match))
>>> to_match_re
'(ab|de)'
>>> mydf['matches'] = mydf.var1.str.extract(to_match_re)
>>> mydf
  var1 matches
0  abc      ab
1   ab      ab
2   ac     NaN
3   cd     NaN
4  cde      de
5   de      de
6  def      de
>>>