FunFormKit converters

One of the nifty things in FunFormKit is the easy-to-use validators, that can also do conversion. Since entering 50 megabytes in bytes is really hard to do, I wrote a simple converter to change '50M' into 52428800.

from FunFormKit.Form import *
from FunFormKit.Field import *
from FunFormKit.Validator import ValidatorConverter

import re
spaces = re.compile(' +')

class TrafficConverter(ValidatorConverter):
    def convert(self, value):
        scales = 'B', 'K', 'M', 'G', 'T'
        value = spaces.sub('', value)
        if value[-1] not in scales:
            return value
        unit = value[-1]
        value = float(value[:-1])

        c = 0
        while scales[c] != unit:
            c = c + 1

        return value * (1024 ** c)

Then, when I set up my form, I just put it in the validators list for my traffic allocation field:

fields = [
    TextField('allocation', size=10, maxLength=20,
        validators = [TrafficConverter()]),
    SubmitButton('submit',
        description='Submit'),
]

formDef = FormDefinition('',  # the form action
    fields, name='form')

I'd previously written a function to pretty-print a bytes value into user-friendly descriptive, so I just use the friendly format when I display it in the field too:

def pretty_traffic(traffic, kilo = 1024.0):
    scales = "B", "K", "M", "G", "T"
    amount = int(traffic)
    for scale in scales:
        if amount < kilo:
            return "%.3f%s" % (amount, scale)
        amount = amount / kilo