折腾：
【未解决】pyppeteer中提取百度搜索结果中的信息
期间，之前调试时可以获取到结果的代码：
resultASelector = "h3[class^='t'] a" searchResultAList = await page.querySelectorAll(resultASelector)
去直接运行，没加断点，结果就找不到结果了：
直接运行，会导致找不到数据
但是也加了await了啊
也没报警告啊
加了断点，等了点时间，就可以找到：
需要搞清楚原因
有个：page.waitForSelector
去看看
有：
“waitFor(selectorOrFunctionOrTimeout: Union[str, int, float], options: dict = None, *args, **kwargs) → Awaitable[T_co]”
和：
“waitForSelector(selector: str, options: dict = None, **kwargs) → Awaitable[T_co]”
但是没有希望的：
waitForSelectorAll
-》看来只能用：
waitForSelector 或 waitFor
去匹配之前的：
【整理】用Chrome或Chromium查看百度首页中各元素的html源码
的：
<span class="nums_text">百度为您找到相关结果约2,370,000个</span>
puppeteer querySelectorAll no result
puppeteer querySelector no result
await page.waitForSelector('div.landscape h3.title'); // <-- add this line //updated from page.waitFor that is getting deprecated in 2020去试试：
await page.waitForSelector('span.nums_text')结果：
直接运行，是可以的
去看看源码：
/Users/crifan/.pyenv/versions/3.6.6/lib/python3.6/site-packages/pyppeteer/page.py
def waitForSelector(self, selector: str, options: dict = None, **kwargs: Any) -> Awaitable: """Wait until element which matches ``selector`` appears on page.
【规避解决】pyppeteer不调试直接运行waitForSelector报错：ElementHandleError Evaluation failed TypeError MutationObserver is not a constructor at pollMutation
此处用代码：
# Method 2: wait element showing
SingleWaitSeconds = 1
while not await page.querySelector(SearchFoundWordsSelector):
print("Still not found %s, wait %s seconds" % (SearchFoundWordsSelector, SingleWaitSeconds))
await asyncio.sleep(SingleWaitSeconds)
# pass算是实现了等待元素出现。
后续即可正常检测到想要的元素了。
【总结】
此处，之所以
await page.querySelectorAll(resultASelector)
获取结果为空
是由于页面还没加载出结果
所以要去等待页面内容，点击搜索按钮后，重启加载完毕
所以最后用代码：
################################################################################
# Wait page reload complete
################################################################################
SearchFoundWordsSelector = 'span.nums_text'
SearchFoundWordsXpath = "//span[@class='nums_text']"
# await page.waitForSelector(SearchFoundWordsSelector)
# await page.waitFor(SearchFoundWordsSelector)
# await page.waitForXPath(SearchFoundWordsXpath)
# Note: all above exception: 发生异常: ElementHandleError Evaluation failed: TypeError: MutationObserver is not a constructor
# so change to following
# # Method 1: just wait
# await page.waitFor(2000) # millisecond
# Method 2: wait element showing
SingleWaitSeconds = 1
while not await page.querySelector(SearchFoundWordsSelector):
print("Still not found %s, wait %s seconds" % (SearchFoundWordsSelector, SingleWaitSeconds))
await asyncio.sleep(SingleWaitSeconds)
# pass即可实现，等待页面中：
<span class="nums_text">百度为您找到相关结果约2,370,000个</span>
的这种元素出现
此处意味着百度搜索结果加载完毕。
后续即可正常搜索到内容了。