将数字写入文件python。 第一次输入不打印

Question

i'm writing numbers to a text file and it works but the issue im having is that it doesn't print the first number.

If I writing 1 2 3 4 5 6 then I have a sentinel loop and use -1 to end.

It would print 2 3 4 5 6

outfile = open("userInput.txt","w")
userInput = int(input("Enter a number to the text file: "))
count = 0
if int(userInput) != -1:
   while(userInput) !=-1:
       userInput = int(input("Enter a number to the text file: "))
       outfile.write(str(userInput) + "\n")
       count+=1
if count == 0:
   print("There is no numbers in the text file")
   outfile.write("There is no numbers in the text file")
count+=1
outfile.close()

Answer 1

You are prompting the user a second time before you write the first input to the file.

See here: (I also simplified your code a little)

outfile = open("userInput.txt","w")
userInput = int(input("Enter a number to the text file: "))
count = 0
while(userInput !=-1): # You don't need the if, because if userInput == -1, this while loop won't run at all
   outfile.write(str(userInput) + "\n") # Swapped these lines so that it would write before asking the user again
   userInput = int(input("Enter a number to the text file: "))
   count+=1
if count == 0:
   print("There is no numbers in the text file")
   outfile.write("There is no numbers in the text file")
outfile.close()

Answer 2

You're asking for new input and writing that before you write the first valid input to the file. Instead, write the valid input first and then ask for input.

outfile = open("userInput.txt","w")
userInput = int(input("Enter a number to the text file: "))
count = 0
while(userInput != -1)
    outfile.write(str(userInput) + "\n")
    userInput = int(input("Enter a number to the text file: "))
    count+=1
if count == 0:
   print("There is no numbers in the text file")
   outfile.write("There is no numbers in the text file")
outfile.close()

This should work.