how to make python request.get wait a few seconds?

问题

I wanted to do get some experience with html crawling, so I wanted to see if I could grab some values of the following site: http://www.iex.nl/Aandeel-Koers/11890/Royal-Imtech/koers.aspx

This site shows the price of imtech shares. If you take a look at the site, you see there is 1 number shown in bold, this is the price of the share.

As you may have seen, this price changes, and that's okay. I only want the value at the time I run my script at this point in time.

but if you reload the page, you may notice how it first shows "laatste koers" and after a delay of 1 second it shows "realtime"

As you may have figured out by now, I'm interested in the "realtime" value.

Here is my question, how do I get this value, I've tried time.sleep(2) on different places. I've tried a timeout at the request. Both didn't work.

How can I fix this?

from lxml import html
import requests

pagina = 'http://www.iex.nl/Aandeel-Koers/11890/Royal-Imtech/koers.aspx'

page = requests.get(pagina)
tree = html.fromstring(page.text)

koers = tree.xpath('//span[@class="RealtimeLabel"]/text()')

prices = tree.xpath('//span[@id="ctl00_ctl00_Content_LeftContent_PriceDetails_lblLastPrice"]/text()')
print koers[0], pagina.split("/")[5], prices[0]

I get output like this

Laatste koers Royal-Imtech 0,093

While I want output like this

Realtime Royal-Imtech 0,093

回答1:

I would suggest use a wait until the element changes.

Find the block of code below to help you.

def wait_while(condition, timeout, delta=1):
    """
    @condition: lambda function which checks if the text contains "REALTIME"
    @timeout: Max waiting time
    @delta: time after which another check has to be made
    """
    max_time = time.time() + timeout
    while max_time > time.time():
        if condition():
            return True
        time.sleep(delta)
    return False

来源：https://stackoverflow.com/questions/26280282/how-to-make-python-request-get-wait-a-few-seconds