在python-ccgi中检测未上载的文件

Question

我试图在提交cgi表单时检测是否上传了可选文件

我读到here我应该做一些类似的事情：

myfile = form["myfile"]
if myfile.file:
    # It's an uploaded file; save it to disk
    file = open('path_to_file','wb')
    file.write(myfile.file.read())
    file.close()

但这对我没用。无论是否上传，文件总是在被写入

对于任何其他字段，我始终可以使用默认值进行检查：

field = cgi.escape(data.getfirst('field','null'))

对于文档中的文件，我看不到解决这个问题的方法。有人帮忙吗

谢谢

Answer 1

我用Firefox进行了测试，上传一个带有空文件输入的表单会导致以下帖子内容：

              -135438447855682763402193870
Content-Disposition: form-data; name="foo"; filename=""
Content-Type: application/octet-stream 

              -135438447855682763402193870 

因此，将上载零长度字段。但是，没有设置文件名，因此改为测试filename属性的值

If a field represents an uploaded file, accessing the value via the value attribute or the getvalue() method reads the entire file in memory as a string. This may not be what you want. You can test for an uploaded file by testing either the filename attribute or the file attribute.