find submit button in selenium without id

There are many options here, to name a few:

If class alone is unique, you can use

driver.find_element_by_css_selector(".button_main").click()

If class + value combo is unique, you can use:

driver.find_element_by_css_selector(".button_main[value='something']").click()

You can also use xpath:

driver.find_element_by_xpath("//input[@type='submit' and @value='something']").click()

If none of those work (i.e. they are not identifying button uniquely), look at the elements above the button (for example <form) and provide the xpath in format:

driver.find_element_by_xpath("//unique_parent//input[@type="submit" and @value='something']").click()

i recommend xpath chrome extension, with it you will be able to get the path by running the extension and shift-clicking on the element you want this chrome extension https://chrome.google.com/webstore/detail/xpath-helper/hgimnogjllphhhkhlmebbmlgjoejdpjl