转换输入字符串:取消列表?

只添加 join 发电机:

df.example = [', '.join(w.replace(' ', '_') for w in re.findall(r"'([^']*)'", x.lower()))
              for x in (df.example)]

print (df)
                                             example
0  adventure, african_elephant, animal, ball_game...

以防万一,熊猫str.join可能对未来有用;-)
1)在示例数据框中添加第二行
2)未修改发电机
3)增加了一行:

    df['example'] = df['example'].str.join(',')

工作示例:

import pandas as pd
import re
d = {
    'example' : pd.Series([
        "['a' 'b c' 'd' 'e f' 'g' 'h i j' 'k l' 'm n']",
        "['a' 'b c' 'd']"
    ]),
}
df = pd.DataFrame(d)
display(df)
    example
0   ['a' 'b c' 'd' 'e f' 'g' 'h i j' 'k l' 'm n']
1   ['a' 'b c' 'd']

df.example = [[w.replace(' ', '_') for w in re.findall(r"'([^']*)'", x.lower())] for x in tqdm(df.example)]
df['example'] = df['example'].str.join(',')
display(df)
    example
0   a,b_c,d,e_f,g,h_i_j,k_l,m_n
1   a,b_c,d