I have one directory where there are only the CSV files I want to use. I want to concatenate all these CSV files and create a bigger one. I've tried one code but it didn't work.

```
import os
import pandas as pd

targetdir = r'C:/Users/toshiba/Documents/ICF2011/Base Admision San Marcos 2014-2/Sabado'

filelist = os.listdir(targetdir) 

big_df=pd.DataFrame()
for file in filelist :
    big_df.append(pd.read_csv(file), ignore_index=True)

```

I run the code and a there's a message that says: `IOError: File A011.csv does not exist`.
This is contradictory because `A011.csv` is the first CSV file in the directory that I used.