Problems with selenium 2 and python 3.4.1 - testing

Question

I have a simple automation to fill login form fields. Actually, it passes good, but there's the problem. I need to see actual output in my console after the script filled fields, like "Logged in successfully" or "Username not found". I tried many stuff, but nothing worked this way, my last try was while loop and it works great, but only when I have positive result. I wrote a second condition, but when I type incorrect data, it drives me crazy to see all these errors in my console. So here's the code and part of output.
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import Select
from selenium.common.exceptions import NoSuchElementException
baseurl = "http://www.somesite/login"
email = input("Type an email: ")
password = input("Type a password: ")
xpaths = { 'loginBox' : "//input[#id='session_email']",
'passwordBox' : "//input[#id='session_password']",
'submitButton' : "//input[#class='ufs-but']",
'success' : "//div[#class='flash-message success']",
'error' : "//span[#class='form_error']"
}
mydriver = webdriver.Firefox()
mydriver.get(baseurl)
mydriver.find_element_by_xpath(xpaths['loginBox']).send_keys(email)
mydriver.find_element_by_xpath(xpaths['passwordBox']).send_keys(password)
mydriver.find_element_by_xpath(xpaths['submitButton']).click()
while mydriver.find_element_by_xpath(xpaths['success']):
print("Success")
if mydriver.find_element_by_xpath(xpaths['error']):
print("No")
And there's what I got when I try to interrupt an error:
File "ab.py", line 32, in <module>
while mydriver.find_element_by_xpath(xpaths['success']):
File "/usr/local/lib/python3.4/site-packages/selenium-2.43.0-py3.4.egg/selenium/webdriver/remote/webdriver.py", line 230, in find_element_by_xpath
return self.find_element(by=By.XPATH, value=xpath)
File "/usr/local/lib/python3.4/site-packages/selenium-2.43.0-py3.4.egg/selenium/webdriver/remote/webdriver.py", line 662, in find_element
{'using': by, 'value': value})['value']
File "/usr/local/lib/python3.4/site-packages/selenium-2.43.0-py3.4.egg/selenium/webdriver/remote/webdriver.py", line 173, in execute
self.error_handler.check_response(response)
File "/usr/local/lib/python3.4/site-packages/selenium-2.43.0-py3.4.egg/selenium/webdriver/remote/errorhandler.py", line 166, in check_response
raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.NoSuchElementException: Message: 'Unable to locate element: {"method":"xpath","selector":"//div[#class=\'flash-message success\']"}' ; Stacktrace:
at FirefoxDriver.prototype.findElementInternal_ (file:///tmp/tmpjax8kj1u/extensions/fxdriver#googlecode.com/components/driver-component.js:9618:26)
at FirefoxDriver.prototype.findElement (file:///tmp/tmpjax8kj1u/extensions/fxdriver#googlecode.com/components/driver-component.js:9627:3)
at DelayedCommand.prototype.executeInternal_/h (file:///tmp/tmpjax8kj1u/extensions/fxdriver#googlecode.com/components/command-processor.js:11612:16)
at DelayedCommand.prototype.executeInternal_ (file:///tmp/tmpjax8kj1u/extensions/fxdriver#googlecode.com/components/command-processor.js:11617:7)
at DelayedCommand.prototype.execute/< (file:///tmp/tmpjax8kj1u/extensions/fxdriver#googlecode.com/components/command-processor.js:11559:5)
As I said, successfull result ain't a problem.
UPD. I corrected the last part of my code a little bit and now I have this:
while mydriver.find_element_by_xpath(xpaths['success']):
print("Success")
break
while mydriver.find_element_by_xpath(xpaths['error']):
print("No")
break
And it works, but not like I want, the output when I want a negative result:
Type an email: w
Type a password: wer
Success
No
As you see, I wanna see 'success' when result is positive and 'no' when it's negative, but I don't want to see them at the same time.
UPD. Props to Macro Giancarli for huge help, so that's how I got what I exactly want:
try:
success = True
success_element = mydriver.find_element_by_xpath(xpaths['success'])
except NoSuchElementException:
success = False
print("Can't log in. Check email and/or password")
try:
failure = True
failure_element = mydriver.find_element_by_xpath(xpaths['error'])
except NoSuchElementException :
failure = False
print("Logged in successfully")

Answer 1

The problem looks like it's in the way you structure your while loop at the end. You shouldn't need to loop in order to check for success or failure.
Consider that there are four outcomes, assuming that you input the login data. You could either find the element that determines success, find the element that determines failure, find both (should be impossible), or find neither (probably in the case of an unexpected screen, or a failure to load the page).
Instead of expecting some values to be returned from the webdriver queries, try putting them in a try block to catch a NoSuchElementException and checking for non-None contents. Also, try handling each of the four cases so that your program will crash less often.
Edit:
Try this.
try:
success = True
success_element = mydriver.find_element_by_xpath(xpaths['success'])
except NoSuchElementException:
success = False
try:
failure = True
failure_element = mydriver.find_element_by_xpath(xpaths['error'])
except NoSuchElementException :
failure = False
# now handle the four possibilities