Python将字典覆盖字典转换为文本文件不起作用…为什么？

Question

I've been previously writing code for a quiz program with a text file that stores all of the participants' results. The code that converts the text file to a dictionary and the text file itself are shown below:

Code:

import collections
from collections import defaultdict
scores_guessed = collections.defaultdict(lambda: collections.deque(maxlen=4))
with open('GuessScores.txt') as f:
    for line in f:
        name,val = line.split(":")
        scores_guessed[name].appendleft(int(val))

for k in sorted(scores_guessed):
    print("\n"+k," ".join(map(str,scores_guessed[k])))

writer = open('GuessScores.txt', 'wb')

for key, value in scores_guessed.items():       
    output = "%s:%s\n" % (key,value)
    writer.write(output)

The text file appears like this:

Jack:10
Dave:20
Adam:30
Jack:40
Adam:50
Dave:60
Jack:70
Dave:80
Jack:90
Jack:100
Dave:110
Dave:120
Adam:130
Adam:140
Adam:150

Now, when I run the program code, the dictionary appears like this:

Adam 150 140 130 50

Dave 120 110 80 60

Jack 100 90 70 40

Now, this arranges the dictionary into order of highest scores, and the top 4 scores!

I want the python IDLE to overwrite the GuessScores.txt to this:

Adam:150
Adam:140
Adam:130
Adam:50
Dave:120
Dave:110
Dave:80
Dave:60
Jack:100
Jack:90
Jack:70
Jack:40

BUT when I run the code, this error appears:

Traceback (most recent call last):
  File "/Users/Ahmad/Desktop/Test Files SO copy/readFile_prompt.py", line 16, in <module>
    writer.write(output)
TypeError: 'str' does not support the buffer interface

The GuessScores.txt file is empty because it cannot write to the file, since there is the error above.

Why is this happening? And what is the fix? I have asked this previously but there were numerous issues. I am running Python 3.3.2 on a Mac 10.8 Mavericks iMac, if that makes any help.

Thanks, Delbert.

Answer 1

The first issue is that you are trying to write text to a file that you opened in binary mode. In 3.x, this will no longer work. "text" vs. "binary" used to mean very little (only affecting line-ending translation, so no difference at all on some systems). Now it means like what it sounds like: a file opened in text mode is one whose contents are to be treated like text with some specific encoding, and a file opened in binary mode is one whose contents are to be treated as a sequence of bytes.

Thus, you need open('GuessScores.txt', 'w') , not open('GuessScores.txt', 'wb') .

That said, you really should be using with blocks to manage the files, and you're going to have to write code that actually formats the dictionary content in the way you want. I assume you intend to output in sorted name order, and you need to iterate over each deque and write a line for each item. Something like:

with open('GuessScores.txt', 'w') as f:
    for name, scores in sorted(scores_guessed.items()):
        for score in scores:
            f.write("{}:{}\n".format(name, score))

(Note also the new-style formatting.)

If necessary, you can explicitly specify the encoding of the file in the open call, with the encoding keyword parameter. (If you don't know what I mean by "encoding", you must learn. I'm serious. Drop everything and look it up.)

Answer 2

The writing problem has to do with the b in your open function. You've opened it in binary mode, so only bytes can be written. You can either remove the b or call bytes on output to give it the right type. You have a logic error anyway though. When I run it on Python 2.7, the output to GuessedScores.txt is this:

Dave:deque([120,110,80,60],maxlen=4)
Jack:deque([100, 90, 70, 40], maxlen=4)
Adam:deque([150, 140, 130, 50], maxlen=4)

So your values are the whole deques, not the individual scores. You'll have to format them, similar to how you did in your print statement.