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python script to open a page and click download

I am trying to open a page and click on download button. It works fine for the pages that have download element but for the pages which doesn't have that element it raises error
Code:
for i in data["allurl"]:
driver.get('{0}'.format(i))
if(driver.find_element_by_id('ContentPlaceHolder1_grdFileUpload_lnkDownload_0')):
button_element = driver.find_element_by_id('ContentPlaceHolder1_grdFileUpload_lnkDownload_0')
button_element.click()
else:
pass
It should pass instead of raising the error but when I run this it says:
NoSuchElementException: Message: no such element: Unable to locate
element:
{"method":"id","selector":"ContentPlaceHolder1_grdFileUpload_lnkDownload_0"}
How do I solve this?

driver.find_element_by_id() doesn't return True or False as your if-statement expects. Either change your if-statement, or use a try/except statement.
from selenium.common.exceptions import NoSuchElementException
for i in data["allurl"]:
driver.get('{0}'.format(i))
try:
button_element = driver.find_element_by_id('ContentPlaceHolder1_grdFileUpload_lnkDownload_0')
button_element.click()
except NoSuchElementException:
pass

Check the length count of the web element.If it is more than 0 then element available and click otherwise it will go to else condition.
for i in data["allurl"]:
driver.get('{0}'.format(i))
if len(driver.find_elements_by_id('ContentPlaceHolder1_grdFileUpload_lnkDownload_0'))>0:
button_element = driver.find_element_by_id('ContentPlaceHolder1_grdFileUpload_lnkDownload_0')
button_element.click()
else:
pass

from selenium.common.exceptions import NoSuchElementException
try:
button_element = driver.find_element_by_id('ContentPlaceHolder1_grdFileUpload_lnkDownload_0')
except NoSuchElementException:
pass
else:
button_element.click()
Note that even if it worked as you expected, it's inefficient because you perform search for the element twice.
EDIT: included the import statement for the exception
UPDATE: as a side note, assuming elements in data["allurl"] are url (i.e. strings) there is no need for string formatting. driver.get(i) would do. And i is poor choice for variable name - better use something more meaningful....

Conditional statement in selenium if element does not exists

I want to check
def first_page_error:
-if the element is not existing "break" and move on with the script
-if element exists then refresh the page
-if element stops existing after the refresh run firstPage()
I will appreciate any help I'm learning python :)
My code right now
def first_page_error():
cap_error = driver.find_element_by_xpath('//*[#id="js-register-with-email"]/div[2]')
while True:
try:
cap_error
except NoSuchElementException:
break
else:
time.sleep(5)
driver.refresh()
def firstPage():
element = driver.find_element_by_xpath('//*[#id="sign-up-link"]')
driver.execute_script("arguments[0].click();", element)
emailInput = driver.find_element_by_xpath('//*[#id="register-email"]')
emailInput.send_keys(emails[0])
condInput = driver.find_element_by_xpath('//*[#id="register-terms"]')
condInput.click()
firstPage()
first_page_error()

A few points of feedback...
If you are automating user scenarios, avoid using JS clicks. A user can't click an element that isn't visible or is covered or is off the screen, etc. Selenium was designed to act like a user and throw errors when a user can't click an element. That's a good thing. It helps you find the problems and solve them as a user would.
Prefer IDs and CSS selectors. They are faster, better supported, and so on. There's a lot of info on the web if you want more explanation. I converted your XPaths that were just locating by ID to *_by_id().
Check for existence by using driver.find_elements_* (Notice the plural, elementS) and check the len of the collection
I would write something like the below.
def first_page_error():
return len(driver.find_elements_by_xpath('//*[#id="js-register-with-email"]/div[2]')) > 0
def firstPage():
driver.find_element_by_id('sign-up-link').click()
driver.find_element_by_id('register-email').send_keys(emails[0])
driver.find_element_by_id('register-terms').click()
firstPage()
if first_page_error():
driver.refresh()
if first_page_error():
firstPage()
# move on with the script

Thank you all for input
I've resolved it with this
def err_redeem_func():
err_redeem = driver.find_element_by_class_name('error')
try:
if err_redeem.is_displayed() and err_redeem.is_enabled():
driver.refresh()
redeem_func()
except NoSuchElementException:
pass
err_redeem_func()

How to put XPath into optional mode

This XPath may available sometime or sometime not.
If reject is true then I am using if statement:
from selenium import webdriver
from selenium.webdriver.support.select import Select
from selenium.webdriver.firefox.options import Options
import time
import bs4
import requests
url="abc"
options = Options()
options.set_preference("dom.webnotifications.enabled", False)
driver=webdriver.Firefox(executable_path="C:\driver\geckodriver.exe",options=options)
driver.get(url)
driver.maximize_window()
reject = driver.find_element_by_xpath("/html/body/div/div/div/main/div/section/div[2]/div[2]/div/ul/a[1]/div[3]/label")
if reject:
driver.find_element_by_xpath("/html/body/div[1]/div/div/main/div/section/div[2]/div[2]/div/ul/a[1]/div[1]/span/i").click()
time.sleep(1)
driver.find_element_by_xpath("/html/body/div[1]/div/div/main/div/section/div[2]/div[2]/div/ul/a[1]/div[1]/div/ul/li[2]").click()
time.sleep(2)
driver.find_element_by_xpath("/html/body/div[3]/div/div/div[3]/button[1]").click()
time.sleep(5)
# Above code blocking to run below code (if reject is None).
neighbourhood= Select(driver.find_element_by_name("Locality"))
neighbourhood.select_by_value("5001641")
But the problem is if this reject variable XPath doesn't exist so it's showing error & blocking below code.
how to make this reject variable optional if XPath available then work if not then leave it & run below code.

You could catch the exception. Something like following:
...
try:
reject = driver.find_element_by_xpath("/html/body/div/div/div/main/div/section/div[2]/div[2]/div/ul/a[1]/div[3]/label")
except:
print("No element found")
if reject:
...
If you need this more often you could create a utility method for that.
def elementVisible(xpath):
try:
driver.find_element_by_xpath(xpath);
return true;
except:
return false;

try-except block will do the trick.
try:
reject = driver.find_element_by_xpath("/html/body/div/div/div/main/div/section/div[2]/div[2]/div/ul/a[1]/div[3]/label")
except:
print("An exception occurred")
Whenever the xpath is not found, the print statement is executed, and further code gets executed without an error like before.

Continue when element is not found in selenium python

The following script follows a page in Instagram:
browser = webdriver.Chrome('./chromedriver')
# GO INSTAGRAM PAGE FOR LOGIN
browser.get('https://www.instagram.com/accounts/login/?hl=it')
sleep(2)
# ID AND PASSWORD
elem = browser.find_element_by_name("username").send_keys('test')
elem = browser.find_element_by_name("password").send_keys('passw')
# CLICK BUTTON AND OPEN INSTAGRAM
sleep(5)
good_elem = browser.find_element_by_xpath('//*[#id="react-root"]/section/main/div/article/div/div[1]/div/form/span/button').click()
sleep(5)
browser.get("https://www.instagram.com")
# GO TO PAGE FOR FOLLOW
browser.get("https://www.instagram.com/iam.ai4/")
sleep(28)
segui = browser.find_element_by_class_name('BY3EC').click()
If an element with class BY3EC isn't found I want the script to keep working.

When an element is not found it throws NoSuchElementException, so you can use try/except to avoid that, for example:
from selenium.common.exceptions import NoSuchElementException
try:
segui = browser.find_element_by_class_name('BY3EC').click()
except NoSuchElementException:
print('Element BY3EC not found') # or do something else here
You can take a look at selenium exceptions to get an idea of what each one of them is for.

surround it with try catches, than you can build a happy path and handle failures as well, so your test case will always work

Best practice is to not use Exceptions to control flow. Exceptions should be exceptional... rare and unexpected. The simple way to do this is to get a collection using the locator and then see if the collection is empty. If it is, you know the element doesn't exist.
In the example below we search the page for the element you wanted and check to see that the collection contains an element, if it does... click it.
segui = browser.find_elements_by_class_name('BY3EC')
if segui:
segui[0].click()

If element does not exist, end the job [Dealing with pagination]

I have a page where the number of elements to loop through is not easily known. As such I’ve made the job loop through Href “a” (364 matches) and when it cannot find the Next button, I am wanting the job to come to an end.
I have tried:
try:
element = driver.find_element_by_xpath('//span[text()="Next Page"]')
except NoSuchElementException:
pass
#except IOError:
#pass
#except OSError:
#pass
As well as other variations and indenting.
My full code is here (it does not allow me to post it here fully due to character limit)

Below code should allow you to close browser and WebDriver session once you reach last page
from selenium.common.exceptions import NoSuchElementException
try:
element = driver.find_element_by_xpath('//span[text()="Next Page"]')
except NoSuchElementException:
driver.quit()