Find character of string using numeric column as index

Question

I know I'm missing something minor so coming here for help rather than keep spinning my wheels -

I've found the index of the character I would like from a string here:

df['letter_idx']= df['string'].str.find(':')-1 

How can I then find the character at this location? (I know below isn't correct, but something like this)

df['letter'] = df['string']['letter_idx']

Is there a simpler way to do this?

Answer 1

You can use the apply method with both "string", "letter_idx" columns.

df["letter"] = df[["string", "letter_idx"]].apply(lambda row: row.string[row.letter_idx], axis=1)

OR you can use the zip function.

>>> df = pandas.DataFrame({"string": ["MyString:123", "Another One: 321"]})
>>> df['letter_idx']= df['string'].str.find(':')-1
>>> df["letter"] = [s[i] for s, i in zip(df.string, df.letter_idx)]
>>> df
             string  letter_idx letter
0      MyString:123           7      g
1  Another One: 321          10      e