使用pd.apply()将列中的每个元素转换为列表，获取第一个元素，并将其转换为datetime

import pandas as pd
from datetime import datetime

df = pd.DataFrame({'column_name': ['2022-01-01', '2022-01-02', '2022-01-03']})

def convert_to_datetime(element):
    element_list = list(element)
    first_element = element_list[0]
    return datetime.strptime(first_element, '%Y-%m-%d')

df['new_column'] = df['column_name'].apply(convert_to_datetime)