pandas增加新列、对列改名字、将两列映射成字典

    df = pd.read_csv(r_f1)
    df['machine_Id'] = df['UserId']+df['knowledge_encoding']
    df.rename(columns={"UserId": "old_UserId","machine_Id":"UserId"},inplace=True)
    df.to_csv(w_f1,index=False)

 把其中的int类型转成字符串

df['date'] = df['year'].map(str)+"/"+df['month'].map(str)+"/"+df['day'].map(str)

将将列映射成字典

df[["a", "b"]].set_index("a").to_dict()["b"]

# output
{1: 'q', 2: 'q', 3: 'w'}

将三列映射成字典

import pandas as pd
from collections import defaultdict

df = pd.DataFrame([[1,"girl","lisa"],[2,"girl","luxi"],[3,"boy","alika"],[4,"boy","join"]],columns = ["id","sex","name"])

result = defaultdict(dict)
for id,sex,name in df.itertuples(index = False):
    result[id][sex] = name

print(result)

# defaultdict(<class 'dict'>, {1: {'girl': 'lisa'}, 2: {'girl': 'luxi'}, 3: {'boy': 'alika'}, 4: {'boy': 'join'}})

把df中a列的空值用b列的值做补充

df['a'][df['a'].isnull()] = df['b'][df['a'].isnull()]