How to add an integer to a string in python - Oanda API

I am trying add a stop loss order along with a buy order using Oanda's REST API. As of right now I can easily specify a price for a stop loss, however, I would like to calculate my stop based on the current price. For instance "current_price" + .1 . I am not very familiar with Python, hence the simple question, but this is driving me nuts. Any help would be appreciated!

I get this error code (along with many others when I try and fix the problem)

trading.py", line 41, in <module>
    stopLoss = float("bid") -- float(.01)
ValueError: could not convert string to float: bid

Thanks in advance, code as follows

trading.py

import Queue
import threading
import time

from execution import Execution
from settings import STREAM_DOMAIN, API_DOMAIN, ACCESS_TOKEN, ACCOUNT_ID
from strategy import TestRandomStrategy
from streaming import StreamingForexPrices


def trade(events, strategy, execution):
    """
    Carries out an infinite while loop that polls the
    events queue and directs each event to either the
    strategy component of the execution handler. The
    loop will then pause for "heartbeat" seconds and
    continue.
    """
    while True:
        try:
            event = events.get(False)
        except Queue.Empty:
            pass
        else:
            if event is not None:
                if event.type == 'TICK':
                    strategy.calculate_signals(event)
                elif event.type == 'ORDER':
                    print "Executing order!"
                    execution.execute_order(event)
        time.sleep(heartbeat)


if __name__ == "__main__":
    heartbeat = 0  # Half a second between polling
    events = Queue.Queue()

    # Trade 1000 unit of EUR/USD
    instrument = "EUR_USD"
    units = 1000
    stopLoss = float("bid") -- float(.01)

    # Create the OANDA market price streaming class
    # making sure to provide authentication commands
    prices = StreamingForexPrices(
        STREAM_DOMAIN, ACCESS_TOKEN, ACCOUNT_ID,
        instrument, events
    )

    # Create the execution handler making sure to
    # provide authentication commands
    execution = Execution(API_DOMAIN, ACCESS_TOKEN, ACCOUNT_ID)

    # Create the strategy/signal generator, passing the
    # instrument, quantity of units and the events queue
    strategy = TestRandomStrategy(instrument, units, events, stopLoss)

    # Create two separate threads: One for the trading loop
    # and another for the market price streaming class
    trade_thread = threading.Thread(target=trade, args=(events, strategy, execution))
    price_thread = threading.Thread(target=prices.stream_to_queue, args=[])

    # Start both threads
    trade_thread.start()
    price_thread.start()

execution.py

import httplib
import urllib


class Execution(object):
    def __init__(self, domain, access_token, account_id):
        self.domain = domain
        self.access_token = access_token
        self.account_id = account_id
        self.conn = self.obtain_connection()

    def obtain_connection(self):
        return httplib.HTTPSConnection(self.domain)

    def execute_order(self, event):
        headers = {
            "Content-Type": "application/x-www-form-urlencoded",
            "Authorization": "Bearer " + self.access_token
        }
        params = urllib.urlencode({
            "instrument" : event.instrument,
            "units" : event.units,
            "type" : event.order_type,
            "side" : event.side,
            "stopLoss" : event.stopLoss

        })
        self.conn.request(
            "POST",
            "/v1/accounts/%s/orders" % str(self.account_id),
            params, headers
        )
        response = self.conn.getresponse().read()
        print response

Event.py

class Event(object):
    pass


class TickEvent(Event):
    def __init__(self, instrument, time, bid, ask):
        self.type = 'TICK'
        self.instrument = instrument
        self.time = time
        self.bid = bid
        self.ask = ask


class OrderEvent(Event):
    def __init__(self, instrument, units, order_type, side, stopLoss):
        self.type = 'ORDER'
        self.instrument = instrument
        self.units = units
        self.order_type = order_type
        self.side = side
        self.stopLoss = stopLoss

Strategy.py

import random

from event import OrderEvent


class TestRandomStrategy(object):
    def __init__(self, instrument, units, events, stopLoss):
        self.instrument = instrument
        self.units = units
        self.events = events
        self.ticks = 0
        self.stopLoss = stopLoss

    def calculate_signals(self, event):
        if event.type == 'TICK':
            self.ticks += 1
            if self.ticks % 1 == 0:
                side = random.choice(["buy"])
                order = OrderEvent(
                    self.instrument, self.units, "market", side, self.stopLoss
                )
                self.events.put(order)

Thanks again..