檔名：test1.txt

檔案內容：

But soft what light through yonder window breaks
It is the east and Juliet is the sun
Arise fair sun and kill the envious moon
Who is already sick and pale with grief

樣例輸出：

PR4E 用 append的寫法：（二重迴圈）

import sys
fname = input("Enter file name: ")
fh = open(fname)
lst = list()
for line in fh:
    line = line.rstrip()
    words = line.split()
    for word in words:
        if word not in lst:
            lst.append(word)
lst.sort()
print(lst)
 

import string
fname = input("Enter file name: ")
fh = open(fname)
l = list()
for line in fh:
    line = line.rstrip()
    l = l +  list(line.split())
s = list(set(l))
s.sort()
print(s)