如何在txt文件中插入一些單詞

Question

現在我想在文件中添加一些單詞，但是我只能通過使用f.open（'xxx.txt'）在文件末尾添加一些單詞（.txt） ，'a'） 如果我使用'a +'模式，這些詞將從頭開始發生。我希望在第一行插入一些句子而不用改變原來的句子。

# using python 2.7.12 
    f = open('Bob.txt','w') 
    f.write('How many roads must a man walk down' 

    ' \nBefore they call him a man' 

    ' \nHow many seas must a white dove sail' 

    ' \nBefore she sleeps in the sand' 

    ' \nHow many times must the cannon balls fly' 

    " \nBefore they're forever banned" 

    " \nThe answer my friend is blowing in the wind" 

    " \nThe answer is blowing in the wind") 
    f.close() 
    # add spice to the song 
    f1 = open('Bob.txt','a') 
    f1.write("\n1962 by Warner Bros.inc.") 
    f1.close() 
    # print song 
    f2 = open('Bob.txt','r') 
    a = f2.read() 
    print a 

我希望在第一行插入「Bob Dylan」，我應該添加什麼代碼？

Answer 1

你不能那樣做。你應該閱讀該文件，修改並重寫它：

with open('./Bob.txt', 'w') as f : 
    f.write('How many roads must a man walk down' 

     ' \nBefore they call him a man' 

     ' \nHow many seas must a white dove sail' 

     ' \nBefore she sleeps in the sand' 

     ' \nHow many times must the cannon balls fly' 

     " \nBefore they're forever banned" 

     " \nThe answer my friend is blowing in the wind" 

     " \nThe answer is blowing in the wind") 
# add spice to the song 
file = [] 
with open('Bob.txt', 'r') as read_the_whole_thing_first: 
    for line in read_the_whole_thing_first : 
     file.append(line) 
file = ["1962 by Warner Bros.inc.\n"] + file 
with open('Bob.txt', 'r+') as f: 
    for line in file: 
     f.writelines(line) 
with open('Bob.txt', 'r') as f2: 
    a = f2.read() 

print a 

結果：

1962 by Warner Bros.inc. 
How many roads must a man walk down 
Before they call him a man 
How many seas must a white dove sail 
Before she sleeps in the sand 
How many times must the cannon balls fly 
Before they're forever banned 
The answer my friend is blowing in the wind 
The answer is blowing in the wind