Import multiple csv files into pandas and concatenate into one DataFrame

Question

I would like to read several csv files from a directory into pandas and concatenate them into one big DataFrame. I have not been able to figure it out though. Here is what I

Answer 1

import glob, os    
df = pd.concat(map(pd.read_csv, glob.glob(os.path.join('', "my_files*.csv"))))

Answer 2

Alternative using the pathlib library (often preferred over os.path).

This method avoids iterative use of pandas concat()/apped().

From the pandas documentation:
It is worth noting that concat() (and therefore append()) makes a full copy of the data, and that constantly reusing this function can create a significant performance hit. If you need to use the operation over several datasets, use a list comprehension.

import pandas as pd
from pathlib import Path

dir = Path("../relevant_directory")

df = (pd.read_csv(f) for f in dir.glob("*.csv"))
df = pd.concat(df)

Answer 3

Almost all of the answers here are either unnecessarily complex (glob pattern matching) or rely on additional 3rd party libraries. You can do this in 2 lines using everything Pandas and python (all versions) already have built in.

For a few files - 1 liner:

df = pd.concat(map(pd.read_csv, ['data/d1.csv', 'data/d2.csv','data/d3.csv']))

For many files:

from os import listdir

filepaths = [f for f in listdir("./data") if f.endswith('.csv')]
df = pd.concat(map(pd.read_csv, filepaths))

---

This pandas line which sets the df utilizes 3 things:

1. Python's map (function, iterable) sends to the function (the pd.read_csv()) the iterable (our list) which is every csv element in filepaths).
2. Panda's read_csv() function reads in each CSV file as normal.
3. Panda's concat() brings all these under one df variable.

Answer 4

This is how you can do using Colab on Google Drive

import pandas as pd
import glob

path = r'/content/drive/My Drive/data/actual/comments_only' # use your path
all_files = glob.glob(path + "/*.csv")

li = []

for filename in all_files:
    df = pd.read_csv(filename, index_col=None, header=0)
    li.append(df)

frame = pd.concat(li, axis=0, ignore_index=True,sort=True)
frame.to_csv('/content/drive/onefile.csv')