Dynamically read and load files into Python - python-3.x

Question

In Python, is there a way to import csv or text files dynamically.We process multiple files a week that have different names and I don't want to update the with open statement manually each time the script runs. I have a function to read the file name which I pass to a variable for later use in my code.
I can see and read the files in the directory but I am not sure if I can add the contents of the folder into a variable that can then be used in the with open statement.
import os
os.chdir('T:\Credit Suite')
DIR = os.listdir()
print(DIR)
import csv,sys
with open('July 19.csv',mode='r') as csv_file:
ROWCOUNT = 0
FILENAME = (csv_file.name)
output = csv.writer(open('test2.txt', 'w', newline=''))
reader =csv.DictReader(csv_file)
for records in reader:
ROWCOUNT += 1
EIN = records['EIN']
DATE = records['Date Established']
DUNS = records['DUNS #']
COMPANYNAME = records['Company Name']
lineout =('<S>'+ EIN+'$EIN '+EIN+'*'+DATE+')'+ COMPANYNAME +'#D-U-N-S '+DUNS).upper()
output.writerow([lineout])
print("writing completed")
I will be running my script when a file hits a folder using a monitor and scheduler in an automated process. I want the code to run no matter what the inbound file name is labeled as in the folder and I wont have to update the code manually for the file name or change the file name to a standard name each time.

Answer 1

os.chdir('T:\Credit Suite')
for root, dirs, files in os.walk("."):
for filename in files:
if filename.endswith('.csv'):
f=filename
import csv,sys
with open(f,mode='r') as csv_file:

Answer 2

os.listdir() returns a list of all the files in the dir, you can just loop all the files:
import os
os.chdir('T:\Credit Suite')
DIR = os.listdir()
print(DIR)
import csv,sys
for file in DIR:
if file.endswith('.csv'):
with open(file,mode='r') as csv_file:
ROWCOUNT = 0
FILENAME = (csv_file.name)
output = csv.writer(open(FILENAME + '_output.txt', 'w', newline=''))
reader =csv.DictReader(csv_file)
all_lines = []
for records in reader:
ROWCOUNT += 1
EIN = records['EIN']
DATE = records['Date Established']
DUNS = records['DUNS #']
COMPANYNAME = records['Company Name']
lineout =('<S>'+ EIN+'$EIN '+EIN+'*'+DATE+')'+ COMPANYNAME +'#D-U-N-S '+DUNS).upper()
all_lines.append(lineout)
output.writerow(all_lines)
print("writing completed")
# remove file to avoid reprocessing the file again in the next run
# of the script, or just move it elsewhere with os.rename
os.remove(file)