为什么不将数据写入创建的文件中？Python

Question

为什么这会创建文件而不将代码写入其中？你知道吗

import os

#List for text
mainlist = []

#Definitions
def main():
  print("Please Input Data(Type 'Done' When Complete):")
  x = input()
  if x.lower() == 'done':
   sort(mainlist)
  else:
    mainlist.append(x)
    main()

def sort(mainlist):
  mainlist = sorted(mainlist, key=str.lower)
  for s in mainlist:
    finalstring = '\n'.join(str(mainlist) for mainlist in mainlist)
  print(finalstring)

  print("What would you like to name the file?:") 
  filename = input()

  with open(filename + ".txt", "w") as f:
    f.write(str(finalstring))

    print("\nPress Enter To Terminate.")
    c = input()  

main()

#Clears to prevent spam.
os.system("cls")

文件被生成，数据被存储。。。但finalstring的内容并没有写进它。文件仍为空。你知道吗

Answer 1

您多次调用sort(mainlist)，每次都会覆盖文件。将打开模式更改为a，如：

with open(filename + ".txt", "a") as f:
    f.write(str(finalstring))

见http://docs.python.org/3.2/tutorial/inputoutput.html#reading-and-writing-files