This answer improves upon prior answers by am05mhz and Javed Karim.
It assumes headless mode, and that a window-size option was not initially set. Before calling this function, ensure the page has loaded fully or sufficiently.
It attempts to set the width and height both to what is necessary. The screenshot of the entire page can sometimes include a needless vertical scrollbar. One way to generally avoid the scrollbar is by taking a screenshot of the body element instead. After saving a screenshot, it reverts the size to what it was originally, failing which the size for the next screenshot may not set correctly.
Ultimately this technique may still not work perfectly well for some examples.
from selenium import webdriver
def save_screenshot(driver: webdriver.Chrome, path: str="/tmp/screenshot.png") -> None:
# Ref: https://stackoverflow.com/a/52572919/
original_size = driver.get_window_size()
required_width = driver.execute_script('return document.body.parentNode.scrollWidth')
required_height = driver.execute_script('return document.body.parentNode.scrollHeight')
driver.set_window_size(required_width, required_height)
# driver.save_screenshot(path) # has scrollbar
driver.find_element_by_tag_name('body').screenshot(path) # avoids scrollbar
driver.set_window_size(original_size['width'], original_size['height'])
If using Python older than 3.6, remove the type annotations from the function definition.