Pandas提取DataFrame中Region对应Name时出现单字符拆分问题

从Pandas DataFrame中提取Region列的唯一值并获取对应Name列数据时，出现异常：当某一Region仅对应一个Name时，该Name会被拆分为单个字符输出（比如linda被拆成l-i-n-d-a）。

相关代码 #

import pandas as pd
data = {
    'Region': ['South','West', 'North','West', 'North',  'South','West', 'North', 'East'],
    'Name': ['Tom', 'nick', 'krish', 'jack','peter','sam','jon','megan','linda']
}

df = pd.DataFrame(data)
list_region = df['Region'].unique().tolist()
for region in list_region:
    list_person = df.set_index('Region').loc[region, 'Name']
    for person in list_person:
        print(region + ' >> ' + person)

异常输出示例 #

North >> megan
East >> l
East >> i
East >> n
East >> d
East >> a

当某个Region只对应一条数据时，df.set_index('Region').loc[region, 'Name']返回的不是Series类型，而是单个字符串对象。遍历字符串时，Python会默认按单个字符拆分，导致输出每个字符。

方案1：强制返回Series类型 #

将region放在列表中传入loc，确保即使只有一条数据，也返回Series对象，遍历的时候就能拿到完整的Name值：

import pandas as pd
data = {
    'Region': ['South','West', 'North','West', 'North',  'South','West', 'North', 'East'],
    'Name': ['Tom', 'nick', 'krish', 'jack','peter','sam','jon','megan','linda']
}

df = pd.DataFrame(data)
list_region = df['Region'].unique().tolist()
for region in list_region:
    # 把region包装成列表，确保返回Series
    list_person = df.set_index('Region').loc[[region], 'Name']
    for person in list_person:
        print(region + ' >> ' + person)

方案2：用groupby分组处理（更简洁） #

直接按Region分组，获取每个组的Name列表，从根源避免类型问题：

import pandas as pd
data = {
    'Region': ['South','West', 'North','West', 'North',  'South','West', 'North', 'East'],
    'Name': ['Tom', 'nick', 'krish', 'jack','peter','sam','jon','megan','linda']
}

df = pd.DataFrame(data)
# 按Region分组，提取每组的Name列表
grouped = df.groupby('Region')['Name'].apply(list)
for region, names in grouped.items():
    for name in names:
        print(f"{region} >> {name}")

方案3：判断返回值类型 #

如果要保留原逻辑，可通过判断list_person的类型，单独处理字符串情况：

import pandas as pd
data = {
    'Region': ['South','West', 'North','West', 'North',  'South','West', 'North', 'East'],
    'Name': ['Tom', 'nick', 'krish', 'jack','peter','sam','jon','megan','linda']
}

df = pd.DataFrame(data)
list_region = df['Region'].unique().tolist()
for region in list_region:
    list_person = df.set_index('Region').loc[region, 'Name']
    # 若为字符串则直接输出，否则遍历Series
    if isinstance(list_person, str):
        print(region + ' >> ' + list_person)
    else:
        for person in list_person:
            print(region + ' >> ' + person)

内容的提问来源于stack exchange，提问作者Guardian Linda