old_contents: import os, sys
  from flask import Flask
  from flask import request
  app = Flask(__name__)
  
  @app.route("/")
  def hello():
      return "Hello World!"
  
  @app.route('/upload', methods=['GET', 'POST'])
  def upload_file():
      if request.method == 'POST':
          f = request.files['file']
          f.save('./uploads/'+f.filename)
      return '',201
  if __name__ == "__main__":
      app.run(host="0.0.0.0", debug=True)
  
  
  @app.route("/listfile")
  def files():
  	path = "./uploads"
  	dircs = os.listdir(path)
  
  
  	for each_file in dircs:
  		files = str(files + each_file + " ")
  	return files
  
new_contents: from flask import Flask
  from flask import request
  import os, sys
  app = Flask(__name__)
  
  @app.route("/")
  def hello():
      return "Hello World!"
  
  @app.route('/upload', methods=['GET', 'POST'])
  def upload_file():
      if request.method == 'POST':
          f = request.files['file']
          f.save('./uploads/'+f.filename)
      return '',201
  if __name__ == "__main__":
      app.run(host="0.0.0.0", debug=True)
  
  
  @app.route("/listfile")
  def files():
  	path = "./uploads"
  	dircs = os.listdir(path)
  
  
  	for each_file in dircs:
  		files = str(files + each_file + " ")
  	return files
  
subject: Fix error1