如何将if elif语句的输出保存到python dataframe中的新变量中？

import pandas as pd

# 创建一个示例DataFrame
data = {'value': [1, 2, 3, 4, 5]}
df = pd.DataFrame(data)

# 创建一个空的列来存储if-elif的结果
df['result'] = None

# 应用if-elif逻辑
for index, row in df.iterrows():
    if row['value'] < 3:
        df.at[index, 'result'] = 'less than 3'
    elif row['value'] < 5:
        df.at[index, 'result'] = 'less than 5'
    else:
        df.at[index, 'result'] = 'greater than or equal to 5'

print(df)

   value         result
0      1  less than 3
1      2  less than 3
2      3  less than 5
3      4  less than 5
4      5  greater than or equal to 5

df['result'] = df['value'].apply(lambda x: 'less than 3' if x < 3 else ('less than 5' if x < 5 else 'greater than or equal to 5'))

df['result'] = df.apply(lambda row: 'less than 3' if pd.notnull(row['value']) and row['value'] < 3 else 
                                      ('less than 5' if pd.notnull(row['value']) and row['value'] < 5 else 
                                       'greater than or equal to 5'), axis=1)