Hello I have data in several excel sheets spread through different subfolders so far I 've been able to write a code that extracts the columns that needed and save them in a dictionary here's the code : 

```
 import os
 import pandas as pd

#Path to file using os

FOLDER_PATH = r'C:\Users\Sarah\Desktop\test'

def listDir(dir):
filenames = os.listdir(dir)
for filename in filenames:
    print('File Name:'+ filename)
    print('folder Path:'+ os.path.abspath(os.path.join(dir, filename)), sep='\n')
listDir(FOLDER_PATH)

#Display sheets names using pandas

pd.set_option('display.width',300)
mosul_file = (r'C:\Users\Sarah\Desktop\test\Months\March.xlsx')
mosul_file2 =(r'C:\Users\Sarah\Desktop\test\Months\April.xlsx')
mosul_file3 =(r'C:\Users\Sarah\Desktop\test\Months\May.xlsx')
mosul_file7 =(r'C:\Users\Sarah\Desktop\test\Months\July.xlsx')
xl = pd.ExcelFile(mosul_file)
xl2 = pd.ExcelFile(mosul_file2)
xl3 = pd.ExcelFile(mosul_file3)
xl7 = pd.ExcelFile(mosul_file7)

 #Display headers index

 mosul_df = xl.parse(0, header=[1], index_col=[0,1,2])
 mosul_df2 = xl2.parse(0, header=[0], index_col=[0,1,2])
 mosul_df3 = xl3.parse(0, header=[0], index_col=[0,1,2])
 mosul_df7 = xl7.parse(1, header=[0], index_col=[0,1,2])

#Read Excel and Select columns

mosul_file = pd.read_excel(r'C:\Users\Sarah\Desktop\test\Months\March.xlsx', sheet_name = 0 , 
index_clo=None, na_values= ['NA'], usecols = "C , F ,G")
mosul_file2 = pd.read_excel(r'C:\Users\Sarah\Desktop\test\Months\April.xlsx', sheet_name = 0 , 
index_clo=None, na_values= ['NA'], usecols = "C , F , G")
mosul_file3 = pd.read_excel(r'C:\Users\Sarah\Desktop\test\Months\May.xlsx', sheet_name = 0 , 
index_clo=None, na_values= ['NA'], usecols = "C , F , G")
mosul_file7 = pd.read_excel(r'C:\Users\Sarah\Desktop\test\Months\July.xlsx', sheet_name = 0 , 
index_clo=None, na_values= ['NA'], usecols = "C, F, G")

#Remove NaN values

data_mosul_df = mosul_file.apply (pd.to_numeric, errors='coerce')
data_mosul_df = mosul_file.dropna()
data_mosul_df2 = mosul_file2.apply (pd.to_numeric, errors='coerce')
data_mosul_df2 = mosul_file2.dropna()
data_mosul_df3 = mosul_file3.apply (pd.to_numeric, errors='coerce')
data_mosul_df3 = mosul_file3.dropna()
data_mosul_df7 = mosul_file3.apply (pd.to_numeric, errors='coerce')
data_mosul_df7 = mosul_file7.dropna()

#Save to Dictionary

datamosul1 = data_mosul_df.to_dict()
datamosul2 = data_mosul_df2.to_dict()
datamosul3 = data_mosul_df3.to_dict()
datamosul7 = data_mosul_df7.to_dict()

```

How to make it automatic so that it loops through all the folders and subfolders?
Thank you