Python fieldstorage file upload

I've tried reading the cgi module's source and found some things about temporary files, but it returns a freaking string, not a file -like object! Inspecting the cgi module description , there is a paragraph discussing how to handle file uploads. 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. You can then read the data at leisure from the file attribute:. Regarding your example, getfirst is just a version of getvalue.

Be warned, that the file is not always created by the cgi module. According to these cgi. So, you have to check if the file was actually created with a query to a custom class' path field like so:. If the Content-Length is also set for the field, which seems rarely, the file should also be created by cgi. That's it. This way you can store the file predictably, decreasing the memory usage footprint of your app.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. How does cgi. FieldStorage store files? Ask Question. Asked 10 years, 5 months ago. Active 6 years, 6 months ago.

Viewed 22k times. Here's the code I've used: import cgi from wsgiref. Improve this question. Justinas Justinas 1 1 gold badge 4 4 silver badges 10 10 bronze badges.

Add a comment. Active Oldest Votes. Improve this answer. Thanks : I'm mostly using Django but sometimes I like to play with those low-level things a little : — Justinas. New in version 3. Since all data provided by the client is consumed at this point, there should be no more than one FieldStorage class instantiated per single request, nor should you make any attempts to read client data before or after instantiating a FieldStorage.

A suggested strategy for dealing with this is that any handler should first check for the existance of a form attribute within the request object. If this exists, it should be taken to be an existing instance of the FieldStorage class and that should be used. If the attribute does not exist and needs to be created, it should be cached as the form attribute of the request object so later handler code can use it.

When the FieldStorage class instance is created, the data read from the client is then parsed into separate fields and packaged in Field objects, one per field. For HTML form inputs of type file , a temporary file is created that can later be accessed via the file attribute of a Field object. The FieldStorage class has a mapping object interface, i. When used as a mapping, the keys are form input names, and the returned dictionary value can be: An instance of StringField , containing the form input value.

This is only when there is a single value corresponding to the input name. StringField is a subclass of str which provides the additional value attribute for compatibility with standard library cgi module. An instance of a Field class, if the input is a file upload. Note: Unlike the standard library cgi module FieldStorage class, a Field object is returned only when it is a file upload. In all other cases the return is an instance of StringField.

This means that you do not need to use the. In addition to standard mapping object methods, FieldStorage objects have the following attributes: list This is a list of Field objects, one for each input. Multiple inputs with the same name will have multiple elements in this list.