迭代列表（1 个列表中的 2 个数据框）

Question

I am importing 2 data frames at the same time:

import pandas as pd
import numpy as np
import time
import glob
import os

msci_folder = 'C:/Users/Mike/Desktop/docs'
mscifile = glob.glob(msci_folder + "/*.csv")

dfs = []
for file in mscifile:
    df = pd.read_csv(file)
    dfs.append(df)

Now I want to apply codes which I was using for every individual data frame, but I get error:

AttributeError: 'list' object has no attribute 'loc'

I try:

for i, df in enumerate(dfs):
    dfs = dfs.loc[dfs['URI'] == '/ID']
    dfs.TIMESTAMP = dfs.TIMESTAMP.apply(lambda x: '%.3f' % x)
    dfs.insert(0, 'Date', 0)
    dfs['Date'] = [x[:8] for x in dfs['TIMESTAMP']]
    dfs.to_csv('C:/Users/Mike/Desktop/docs/test.csv', index=False) 

Answer 1

In your second for loop:

for i, df in enumerate(dfs):
    dfs = dfs.loc[dfs['URI'] == '/ID']
    dfs.TIMESTAMP = dfs.TIMESTAMP.apply(lambda x: '%.3f' % x)
    dfs.insert(0, 'Date', 0)
    dfs['Date'] = [x[:8] for x in dfs['TIMESTAMP']]
    dfs.to_csv('C:/Users/Mike/Desktop/docs/test.csv', index=False) 

you used dfs , which is the initial list you created, hence the error. You should change every instance of dfs inside that for loop with df .

for i, df in enumerate(dfs):
    # dfs = dfs.loc[dfs['URI'] == '/ID']
    df = df.loc[df['URI'] == '/ID']

    # ... and so on

    # save to different files
    df.to_csv(f'C:/Users/Mike/Desktop/docs/test_{i}.csv', index=False)