Can someone help me understand why my code fails to find the element by ID. Code below:

from selenium import webdriver
driver=webdriver.Firefox()
driver.get('https://app.waitwhile.com/checkin/lltest3/user')
element = driver.find_element_by_id("guestPhone")

Inspecting element shows the ID clearly.

<input type="tel" name="guestPhone" id="guestPhone" class="form-control ng-pristine ng-empty ng-invalid ng-invalid-phone-validator ng-invalid-required ng-touched" ng-model="form.model" ng-model-options="{ 'updateOn': 'default blur', 'debounce': { 'default': 350, 'blur': 0 } }" uib-typeahead="guest.phone for guest in form.onChange({value:$viewValue})" typeahead-min-length="6" typeahead-on-select="form.onSelect({guest:$item})" typeahead-select-on-exact="true" uib-tooltip="Please enter valid number. Include country code for non-US numbers" tooltip-trigger="'none'" tooltip-is-open="(form.guestForm.$submitted || form.guestForm.guestPhone.$touched) &amp;&amp; form.guestForm.guestPhone.$invalid" tooltip-placement="bottom" ng-required="::form.required" phone-validator="US" placeholder="Mobile phone" title="Please enter a valid phone number" autocomplete="nope" next-on-enter="" aria-autocomplete="list" aria-expanded="false" aria-owns="typeahead-47-2884" required="required" style="">

P.S. I've also tried XPath and name as well. Still no luck.

You need to wait for the element to become visible on the page. You can tell this is loaded in dynamically because if you right-click on the page in chrome and view source you'll see there's no guestPhone element. It gets loaded in with javascript

Here's an example from http://isaacviel.name/make-web-driver-wait-element-become-visiable/:

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as ECdriver = webdriver.Firefox()
driver.get("http://somedomain/url_that_delays_loading")
try:element = WebDriverWait(driver, 10).until(EC.visibility_of_element_located((By.ID, "myDynamicElement")))
finally:driver.quit()