infoFile = ‘E:/userinfo.txt‘  # \\或者/

i = 0
for i in range(3):
	flag = True
	username = input(‘please inupt username:‘).strip()
	passwd = input(‘please inupt passwd:‘)
	confirm_passwd = input(‘please inupt confirm_passwd:‘)
	with open(infoFile, ‘r‘) as f:
		# f.seek(0)
		for line in f.readlines():
			user, pwd = line.strip().split(‘,‘)
			if user == username:
				print(‘username is already exist.‘)
				i += 1
				flag = False				
				break
	if flag == True:	
		if passwd != confirm_passwd:
			print(‘passwd is unequall.‘)
			i += 1
		else:
			print(‘register success.‘)
			with open(infoFile, ‘a‘) as f2:
				f2.write(‘\n‘ + username + ‘,‘ + passwd)
			break
else:
	print(‘over, try next day.‘)

註冊（文件操作）