How to put a limit on upload size

Problem

How to put a limit on upload size

Solution

web.py uses cgi module to parse user inputs and the cgi module has a provision to limit max size of input.

The following code limits the size of input data to 10MB.

import cgi

# Maximum input we will accept when REQUEST_METHOD is POST
# 0 ==> unlimited input
cgi.maxlen = 10 * 1024 * 1024 # 10MB

Please note that this limits the size of POST data, not file uploaded. However they will be almost same if there is no other input.

The cgi module raises ValueError when the input size is more than cgi.maxlen. It can be caught to display required error message.

class upload:
    def POST(self):
        try:
            i = web.input(file={})
        except ValueError:
            return "File too large"