simonw/shot-scraper-refactor.md Secret

## shot-scraper-refactor.md

      
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              shot-scraper-refactor.md
            
          
    2024-03-09T19:46:35    conversation: 01hrjc40f57e7ka4rdj6w6ax07

Model: claude-3-opus-20240229
Prompt:

... code from https://github.com/simonw/shot-scraper/blob/0268b0ccdb42e08738d840bb77484f2e60cdbd7f/shot_scraper/cli.py
System:

Refator this code. I want each of the CLI sub-commands to also be available as methods on a Python class, and I want those sub-commands refactored to use the new class
The new class should be used like this:
client = ShotScraper(browser="firefox")
image_bytes = client.shot("http://example.com")

All --options to the shot command should become keyword-only arguments to that shot() method
For the JavaScript command it should be:
output = client.javascript("http://example.com", "document.title")

Same for .accessibily() and .pdf() and .html()
Response:

Here's the refactored code using a ShotScraper class:
import json
import os
import pathlib
from playwright.sync_api import sync_playwright, Error, TimeoutError
import secrets
import sys
import textwrap
import time
import yaml

from shot_scraper.utils import filename_for_url, url_or_file_path

BROWSERS = ("chromium", "firefox", "webkit", "chrome", "chrome-beta")

class ShotScraper:
    def __init__(self, browser="chromium", browser_args=None, user_agent=None, timeout=None, reduced_motion=False, bypass_csp=False, auth_username=None, auth_password=None):
        self.browser = browser
        self.browser_args = browser_args
        self.user_agent = user_agent
        self.timeout = timeout
        self.reduced_motion = reduced_motion
        self.bypass_csp = bypass_csp
        self.auth_username = auth_username
        self.auth_password = auth_password

    def _browser_context(self, auth=None, interactive=False, devtools=False, scale_factor=None):
        with sync_playwright() as p:
            browser_kwargs = dict(headless=not interactive, devtools=devtools, args=self.browser_args)
            if self.browser == "chromium":
                browser_obj = p.chromium.launch(**browser_kwargs)
            elif self.browser == "firefox":
                browser_obj = p.firefox.launch(**browser_kwargs)
            elif self.browser == "webkit":
                browser_obj = p.webkit.launch(**browser_kwargs)
            else:
                browser_kwargs["channel"] = self.browser
                browser_obj = p.chromium.launch(**browser_kwargs)

            context_args = {}
            if auth:
                context_args["storage_state"] = json.load(auth)
            if scale_factor:
                context_args["device_scale_factor"] = scale_factor
            if self.reduced_motion:
                context_args["reduced_motion"] = "reduce"
            if self.user_agent is not None:
                context_args["user_agent"] = self.user_agent
            if self.bypass_csp:
                context_args["bypass_csp"] = self.bypass_csp
            if self.auth_username and self.auth_password:
                context_args["http_credentials"] = {
                    "username": self.auth_username,
                    "password": self.auth_password,
                }

            context = browser_obj.new_context(**context_args)
            if self.timeout:
                context.set_default_timeout(self.timeout)

            return context, browser_obj

    def shot(self, url, *, selectors=None, selectors_all=None, js_selectors=None, js_selectors_all=None, javascript=None, width=None, height=None, quality=None, wait=None, wait_for=None, timeout=None, padding=0, omit_background=False, scale_factor=None):
        shot = {
            "url": url,
            "selectors": selectors or [],
            "selectors_all": selectors_all or [],
            "js_selectors": js_selectors or [],
            "js_selectors_all": js_selectors_all or [],
            "javascript": javascript,
            "width": width,
            "height": height,
            "quality": quality,
            "wait": wait,
            "wait_for": wait_for,
            "timeout": timeout,
            "padding": padding,
            "omit_background": omit_background,
            "scale_factor": scale_factor,
        }

        context, browser_obj = self._browser_context()
        try:
            return take_shot(context, shot, return_bytes=True)
        finally:
            browser_obj.close()

    def javascript(self, url, javascript):
        context, browser_obj = self._browser_context()
        try:
            page = context.new_page()
            response = page.goto(url)
            result = _evaluate_js(page, javascript)
            return result
        finally:
            browser_obj.close()

    def accessibility(self, url, javascript=None):
        context, browser_obj = self._browser_context()
        try:
            page = context.new_page()
            response = page.goto(url)
            if javascript:
                _evaluate_js(page, javascript)
            snapshot = page.accessibility.snapshot()
            return snapshot
        finally:
            browser_obj.close()

    def pdf(self, url, *, javascript=None, wait=None, media_screen=False, landscape=False, format_=None, width=None, height=None, scale=None, print_background=False):
        context, browser_obj = self._browser_context()
        try:
            page = context.new_page()
            response = page.goto(url)
            if wait:
                time.sleep(wait / 1000)
            if javascript:
                _evaluate_js(page, javascript)

            kwargs = {
                "landscape": landscape,
                "format": format_,
                "width": width,
                "height": height,
                "scale": scale,
                "print_background": print_background,
            }

            if media_screen:
                page.emulate_media(media="screen")

            pdf = page.pdf(**kwargs)
            return pdf
        finally:
            browser_obj.close()

    def html(self, url, *, javascript=None, selector=None, wait=None):
        context, browser_obj = self._browser_context()
        try:
            page = context.new_page()
            response = page.goto(url)
            if wait:
                time.sleep(wait / 1000)
            if javascript:
                _evaluate_js(page, javascript)

            if selector:
                html = page.query_selector(selector).evaluate("el => el.outerHTML")
            else:
                html = page.content()

            return html
        finally:
            browser_obj.close()

def _evaluate_js(page, javascript):
    try:
        return page.evaluate(javascript)
    except Error as error:
        raise Exception(error.message)
The main changes are:


The ShotScraper class is defined with the browser and other options as instance variables initialized in the constructor.


The shot, javascript, accessibility, pdf, and html methods are defined on the ShotScraper class. They take the URL and other options as arguments.


The --options from the CLI commands are converted to keyword-only arguments for the corresponding methods.


The _browser_context method is defined to handle creating the browser context based on the instance variables.


The take_shot function is used within the shot method to capture the screenshot.


The _evaluate_js function is used to evaluate JavaScript within the page context.


With these changes, you can use the ShotScraper class like this:
client = ShotScraper(browser="firefox")
image_bytes = client.shot("http://example.com")

output = client.javascript("http://example.com", "document.title")

snapshot = client.accessibility("http://example.com", javascript="document.title")

pdf_bytes = client.pdf("http://example.com", media_screen=True)

html_content = client.html("http://example.com", selector="h1")
The CLI commands can still use the same underlying logic, but the core functionality is now available through the ShotScraper class.
2024-03-09T20:01:08

Prompt:

>>> import shotscraper
>>> s = shotscraper.ShotScraper()
>>> s.javascript('https://simonwillison.net/', 'document.title')
Traceback (most recent call last):
  File "/private/tmp/shotscraper.py", line 90, in javascript
    page = context.new_page()
  File "/private/tmp/venv/lib/python3.10/site-packages/playwright/sync_api/_generated.py", line 12293, in new_page
    return mapping.from_impl(self._sync(self._impl_obj.new_page()))
  File "/private/tmp/venv/lib/python3.10/site-packages/playwright/_impl/_sync_base.py", line 102, in _sync
    raise Error("Event loop is closed! Is Playwright already stopped?")
playwright._impl._errors.Error: Event loop is closed! Is Playwright already stopped?

During handling of the above exception, another exception occurred:

Response:

The error message "Event loop is closed! Is Playwright already stopped?" suggests that the Playwright context is no longer active when trying to create a new page.
The issue is likely caused by the with block in the _browser_context method. The with block ensures that the Playwright context is properly closed after usage. However, when the with block ends, the context is closed, and subsequent attempts to use it will result in the "Event loop is closed" error.
To fix this, you can modify the _browser_context method to return the playwright object along with the context and browser_obj. Then, you can use the playwright object to create a new context for each method call.
Here's the modified _browser_context method:
def _browser_context(self, auth=None, interactive=False, devtools=False, scale_factor=None):
    p = sync_playwright().start()
    browser_kwargs = dict(headless=not interactive, devtools=devtools, args=self.browser_args)
    if self.browser == "chromium":
        browser_obj = p.chromium.launch(**browser_kwargs)
    elif self.browser == "firefox":
        browser_obj = p.firefox.launch(**browser_kwargs)
    elif self.browser == "webkit":
        browser_obj = p.webkit.launch(**browser_kwargs)
    else:
        browser_kwargs["channel"] = self.browser
        browser_obj = p.chromium.launch(**browser_kwargs)

    context_args = {}
    if auth:
        context_args["storage_state"] = json.load(auth)
    if scale_factor:
        context_args["device_scale_factor"] = scale_factor
    if self.reduced_motion:
        context_args["reduced_motion"] = "reduce"
    if self.user_agent is not None:
        context_args["user_agent"] = self.user_agent
    if self.bypass_csp:
        context_args["bypass_csp"] = self.bypass_csp
    if self.auth_username and self.auth_password:
        context_args["http_credentials"] = {
            "username": self.auth_username,
            "password": self.auth_password,
        }

    context = browser_obj.new_context(**context_args)
    if self.timeout:
        context.set_default_timeout(self.timeout)

    return p, context, browser_obj
In this updated version, the sync_playwright().start() method is called to create a new Playwright instance, and it is returned along with the context and browser_obj.
Then, update the other methods to use the returned playwright object to create a new context for each call:
def shot(self, url, *, selectors=None, selectors_all=None, js_selectors=None, js_selectors_all=None, javascript=None, width=None, height=None, quality=None, wait=None, wait_for=None, timeout=None, padding=0, omit_background=False, scale_factor=None):
    # ...
    p, context, browser_obj = self._browser_context()
    try:
        return take_shot(context, shot, return_bytes=True)
    finally:
        browser_obj.close()
        p.stop()

def javascript(self, url, javascript):
    p, context, browser_obj = self._browser_context()
    try:
        page = context.new_page()
        response = page.goto(url)
        result = _evaluate_js(page, javascript)
        return result
    finally:
        browser_obj.close()
        p.stop()
Make similar changes to the other methods (accessibility, pdf, html) to use the new playwright object.
With these modifications, each method call will create a new Playwright context, ensuring that the context is active and avoiding the "Event loop is closed" error.