Question

我有分数文件：

Foo 12
Bar 44

我尝试对它进行排序，擦除它，然后将排序的分数写入其中。但我得到错误：

ValueError：关闭文件的I / O操作

这是我的功能：

def Sort():
scores = []
with open("results.txt") as x:
    for linia in x:
        name,score=linia.split(' ')
        score=int(score)
        scores.append((name,score))
    scores.sort(key=lambda sc: sc[1])
x.truncate()
for name, score in scores:
    x.write(name+' '+str(score))

Answer 1

该文件仅在内部 with块中保持打开状态。之后，Python将自动关闭它。您需要使用第二个with块再次打开它。

def Sort():
    scores = []
    with open("results.txt") as x:
        # x is open only inside this block!
        for linia in x:
            name, score=linia.split(' ')
            score = int(score)
            scores.append((name, score))
        scores.sort(key=lambda sc: sc[1])

    with open("results.txt", "w") as x:
        # open it a second time, this time with `w`
        for name, score in scores:
            x.write(name + ' ' + str(score))

Sort()

这也可以仅使用一个文件打开来完成。在这种情况下，您以双读/写模式（r +）打开文件，并使用truncate删除以前的文件内容。

def Sort():
    scores = []
    with open("results.txt", "r+") as x:
        for linia in x:
            name, score = linia.split(' ')
            score = int(score)
            scores.append((name, score))
        scores.sort(key=lambda sc: sc[1])

        # Go to beginning of file
        x.seek(0)

        # http://devdocs.io/python~3.5/library/io#io.IOBase.truncate
        # If no position is specified to truncate, 
        # then it resizes to current position

        x.truncate()
        # note that x.truncate(0) does **not** work,
        # without an accompanying call to `seek`.
        # a number of control characters are inserted
        # for reasons unknown to me.

        for name, score in scores:
            x.write(name + ' ' + str(score) + '\n')

然而，就个人而言，我觉得第一种方法更好，而且你不太可能用脚射击自己。

Python文件读写

1 个答案: