当文件小于 1kByte 时，cStringIO.StringO 无法保存上传的文件流

Question

我借用了这段代码来将文件流保存到磁盘，除了文件大小小于 1kb 时，它都可以工作。我收到此错误：

in stuff_uploaded:
copy(theFile.file.name, './tmp/'+theFile.filename) #saves temporary file to /cp2/tmp/

AttributeError: 'cStringIO.StringO' 对象没有属性 'name'

@cherrypy.expose
@cherrypy.tools.noBodyProcess()
def stuff_uploaded(self, theFile=None):
    import cgi
    import tempfile
    # convert the header keys to lower case
    lcHDRS = {key.lower():val for key, val in cherrypy.request.headers.iteritems()}
    class myFieldStorage(cgi.FieldStorage):
        """uses a named temporary file instead of the default non-named file; keeping it visibile (named), allows us to create a
        2nd link after the upload is done, thus avoiding the overhead of making a copy to the destination filename."""
        def make_file(self, binary=None):
            return tempfile.NamedTemporaryFile()
    formFields = myFieldStorage(fp=cherrypy.request.rfile,
                                headers=lcHDRS,
                                environ={'REQUEST_METHOD':'POST'},
                                keep_blank_values=True)
    theFile = formFields['theFile']
    # we now create a 2nd link to the file, using the submitted filename.
    from shutil import copy
    copy(theFile.file.name, './tmp/'+theFile.filename) #saves temporary file 
    msgs = csv_to_survey.match_fieldnames('./tmp/'+theFile.filename)
    return './tmp/'+theFile.filename

那么我能做些什么来确保 cStringIO.StringO 处理上传的小文件呢？

Answer 1

直接打开写入文件即可：

with open('./tmp/'+theFile.filename, "w") as f:
    f.write(theFile.file.getvalue())

或者不管文件在磁盘上还是StringIO都处理它，把它当成类文件对象：

import shutil

with open('./tmp/'+theFile.filename, "w") as f:
    # If the file pointer might not be at the beginning of theFile.file, add:
    # theFile.file.seek(0)
    shutil.copyfileobj(theFile.file, f)
    # While:
    #     f.write(theFile.file.read())
    # would work most of the time, it involves holding the whole contents of the
    # file in memory at once (which you want to avoid; that's why CherryPy
    # uses temp files for larger data). shutil.copyfileobj does block by
    # block copies, which have fixed peak memory usage while still running
    # (almost) as fast

注意：这（以及您的原始解决方案）是不安全的，因为两次上传相同的文件将覆盖以前的文件，并且（取决于名称上的服务器过滤器）文件名可能会遍历文件系统以覆盖 tmp 之外的意外文件目录。