How to import multiple csv files and concatenate into one DataFrame using pandas

Question

I have problem No objects to concatenate. I can not import .csv files from main and its subdirectories to concatenate them into one DataFrame. I am using pandas. Old answers did not help me so please do not mark as duplicated.

Folder structure is like that

main/*.csv
main/name1/name1/*.csv
main/name1/name2/*.csv
main/name2/name1/*.csv
main/name3/*.csv

import pandas as pd
import os
import glob

folder_selected = 'C:/Users/jacob/Documents/csv_files'

1. not works

frame = pd.concat(map(pd.read_csv, glob.iglob(os.path.join(folder_selected, "/*.csv"))))

2. not works

csv_paths = glob.glob('*.csv')
dfs = [pd.read_csv(folder_selected) for folder_selected in csv_paths]
df = pd.concat(dfs)

3. not works

            all_files = []
            
            all_files = glob.glob (folder_selected + "/*.csv")
            
            file_path = []
            for file in all_files:
                df = pd.read_csv(file, index_col=None, header=0)
                file_path.append(df)
                    
        frame = pd.concat(file_path, axis=0, ignore_index=False)

Answer 1

You need to search the subdirectories recursively.

folder = 'C:/Users/jacob/Documents/csv_files'
path = folder+"/**/*.csv"

1. Using glob.iglob

df = pd.concat(map(pd.read_csv, glob.iglob(path, recursive=True)))

2. Using glob.glob

csv_paths = glob.glob(path, recursive=True)
dfs = [pd.read_csv(csv_path) for csv_path in csv_paths]
df = pd.concat(dfs)

3. Using os.walk

file_paths = []
for base, dirs, files in os.walk(folder):
    for file in fnmatch.filter(files, '*.csv'):
        file_paths.append(os.path.join(base, file))
df = pd.concat([pd.read_csv(file) for file in file_paths])

4. Using pathlib

from pathlib import Path
files = Path(folder).rglob('*.csv')
df = pd.concat(map(pd.read_csv, files))

Answer 2

Check Dask Library as following, which reads many files to one df

>>> import dask.dataframe as dd
>>> df = dd.read_csv('data*.csv')

Read their docs https://examples.dask.org/dataframes/01-data-access.html#Read-CSV-files