文件处理，写作，阅读 [英] File Handling, Writing, Reading

问题描述

我偶然发现了文件处理问题，
第二行无缘无故地为您提供了9的值，
第三行给出了一个错误io.UnsupportedOperation：不可读

I stumbled across an issue of file handling, second line gives you an value of 9 for no reason, third line gives an Error io.UnsupportedOperation: not readable

c = open("Test.txt", "w+")
c.write("Hey there")
content = c.read()
c.close

print (content)

我该如何解决？

推荐答案

第二行无缘无故为9

Second Line gives you an value of 9 for no reason

write（） 函数。该值是写入文件的字符数。

That is the return value from the write() function in Python 3. The value is the number of characters written to the file.

第三行给出错误io.UnsupportedOperation：不可读

Third Line gives an Error io.UnsupportedOperation: not readable

不确定您在这里做了什么。在 write（）之后，文件指针位于文件的末尾。如果您确实使用 w + 打开了文件，则应该看不到错误，但是应该从文件中读取0个字符。如果您以 w 模式打开文件，则将得到 io.UnsupportedOperation 异常，因为未打开文件阅读。检查您在测试时使用的模式。

Not sure what you've done here. Following the write(), the file pointer is positioned at the end of the file. If you really opened the file with w+ then you should not see an error, but 0 characters should be read from the file. If you opened the file with mode w, then you would get the io.UnsupportedOperation exception because the file is not opened for reading. Check which mode you used when you tested.

尝试以下操作：

with open('Test.txt', 'w+') as c:
    n = c.write("Hey there")
    print('Wrote {} characters to file'.format(n))

    content = c.read()
    print('Read {} characters from file'.format(len(content)))
    print('{!r}'.format(content))

    _ = c.seek(0)    # move file pointer back to the start of the file
    content = c.read()
    print('After seeking to start, read {} characters from file'.format(len(content)))
    print('{!r}'.format(content))

输出：

Wrote 9 characters to file
Read 0 characters from file
''
After seeking to start, read 9 characters from file
'Hey there'

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