用正则表达式替换 pandas 列值中字符串的开头或结尾

Question

With sed, I can do

$ sed 's/^/prefix/' <<EOF
> foo
> EOF
prefixfoo

When I use pandas.Series.str.replace , the regex does not work. The minimal working example

import pandas as pd

df = pd.DataFrame({"text": ["foo", "bar"]})
df.text.str.replace("^", "prefix", regex=True)

returns

0    foo
1    bar
Name: text, dtype: object

Answer 1

It works if you capture the ^ :

df['text'].str.replace(r'(^)', 'prefix', regex=True)

Output:

0    prefixfoo
1    prefixbar
Name: text, dtype: object

That said the best method to prepend a string would be to concatenate:

'prefix'+df['text']