《最新出炉》系列小成篇-Python+Playwright自动化测试-66 - 等待元素至指定状态(出现、移除、显示和隐藏)

1.简介

在我们日常工作中进行UI自动化测试时，保证测试的稳定性至关重要。其中一个关键方面是正确地定位和操作网页中的元素。在网页中，元素可能处于不同的状态，有些可能在页面加载完成之前不在DOM中，需要某些操作后才会出现，而其他元素可能一直存在于DOM中，但最初处于隐藏状态，需要通过操作才能使其出现进而处于可见状态。 因此如果在执行脚本时没有考虑到元素的状态，很可能导致脚本执行失败。为了保证自动化测试的稳定性，我们需要确保在执行操作之前，所需的元素已经达到了指定状态。

下面宏哥将介绍和分析讲解三种常用的元素等待方式：wait_for_timeout()，wait_for()，wait_for_selector() 和 wait_for_element_state()以及四者之间的优劣势。

2.强制等待

2.1wait_for_timeout()

wait_for_timeout() 方法会等待调用方法时指定的时间。‌

这个方法用于设置一个等待的超时时间，‌它允许程序在执行某些操作前等待指定的时间。‌如果在设定的时间内操作未完成，‌则可能会抛出超时错误。‌这种机制在编程中非常有用，‌尤其是在需要等待某个条件满足或资源可用时。‌例如，‌在使用playwright进行网页自动化测试时，‌wait_for_timeout()方法可以用来确保在继续执行操作之前，‌网页元素已经加载完成或处于可操作状态。‌如果元素未在给定的时间内加载完成，‌则可以通过捕获超时错误来处理这种情况，‌从而避免操作失败。官方定义的函数如下：

    def wait_for_timeout(self, timeout: float) -> None:
        """Page.wait_for_timeout

        Waits for the given `timeout` in milliseconds.

        Note that `page.waitForTimeout()` should only be used for debugging. Tests using the timer in production are going
        to be flaky. Use signals such as network events, selectors becoming visible and others instead.

        **Usage**

        ```py
        # wait for 1 second
        await page.wait_for_timeout(1000)
        ```

        ```py
        # wait for 1 second
        page.wait_for_timeout(1000)
        ```

        Parameters
        ----------
        timeout : float
            A timeout to wait for
        """

        return mapping.from_maybe_impl(
            self._sync(self._impl_obj.wait_for_timeout(timeout=timeout))
        )

3.自动等待

3.1.wait_for()

wait_for() 是先定位元素，再等待元素满足指定状态。先定位元素，再使用wait_for() 方法也可以等待元素到达指定的状态。

如果元素已满足条件，则立即返回。否则，它会等待直到超时时间到达为止。

该方法接受两个关键字参数：
timeout：指定最大等待时间（以毫秒为单位）。默认为 30000（30秒），但可以更改。
state：指定要等待的状态。默认为 ‘visible’。可以是 ‘attached’、‘detached’、‘hidden’ 或 ‘visible’ 中的一个。

官方定义的函数如下：

    def wait_for(
        self,
        *,
        timeout: typing.Optional[float] = None,
        state: typing.Optional[
            Literal["attached", "detached", "hidden", "visible"]
        ] = None
    ) -> None:
        """Locator.wait_for

        Returns when element specified by locator satisfies the `state` option.

        If target element already satisfies the condition, the method returns immediately. Otherwise, waits for up to
        `timeout` milliseconds until the condition is met.

        **Usage**

        ```py
        order_sent = page.locator(\"#order-sent\")
        await order_sent.wait_for()
        ```

        ```py
        order_sent = page.locator(\"#order-sent\")
        order_sent.wait_for()
        ```

        Parameters
        ----------
        timeout : Union[float, None]
            Maximum time in milliseconds. Defaults to `30000` (30 seconds). Pass `0` to disable timeout. The default value can
            be changed by using the `browser_context.set_default_timeout()` or `page.set_default_timeout()` methods.
        state : Union["attached", "detached", "hidden", "visible", None]
            Defaults to `'visible'`. Can be either:
            - `'attached'` - wait for element to be present in DOM.
            - `'detached'` - wait for element to not be present in DOM.
            - `'visible'` - wait for element to have non-empty bounding box and no `visibility:hidden`. Note that element
              without any content or with `display:none` has an empty bounding box and is not considered visible.
            - `'hidden'` - wait for element to be either detached from DOM, or have an empty bounding box or
              `visibility:hidden`. This is opposite to the `'visible'` option.
        """

        return mapping.from_maybe_impl(
            self._sync(self._impl_obj.wait_for(timeout=timeout, state=state))
        )

宏哥还是按之前toast的消息那个demo来演示，这里就不写demo的HTML代码，不知道的可以看宏哥之前的文章：传送门

3.1.1代码设计

3.1.2参考代码

# coding=utf-8🔥

# 1.先设置编码，utf-8可支持中英文，如上，一般放在第一行

# 2.注释：包括记录创建时间，创建人，项目名称。
'''
Created on 2024-07-16
@author: 北京-宏哥
北京宏哥（微信搜索：北京宏哥，关注宏哥，提前解锁更多测试干货！）
Project: 《最新出炉》系列小成篇-Python+Playwright自动化测试-66 - 等待元素至指定状态
'''

# 3.导入模块
from playwright.sync_api import Playwright, sync_playwright, expect

def run(playwright: Playwright) -> None:

    browser = playwright.chromium.launch(headless=False)
    context = browser.new_context()
    page = context.new_page()
    page.goto("E:/Desktop/test/toast.html")
    # 点击 点击关注 按钮
    page.locator("#hongge").click()
    # 等待元素出现在dom
    page.locator('//html/body/div').wait_for(state="attached")
    # 获取元素文本
    print(page.locator('//html/body/div').inner_text())
    page.locator('//html/body/div').wait_for(state="detached")
    print("元素已经从DOM移除")
    page.wait_for_timeout(1000)
    context.close()
    browser.close()

with sync_playwright() as playwright:
    run(playwright)

3.1.3运行代码

1.运行代码，右键Run'Test'，就可以看到控制台输出，如下图所示：

2.运行代码后电脑端的浏览器的动作。如下图所示：

3.2wait_for_selector()

page.wait_for_selector() 是 Playwright 中的一个方法，‌用于等待与指定 CSS 选择器匹配的元素出现在页面中。‌

这个方法接受一个选择器参数和一个可选的选项参数。‌常用的选项参数包括：‌

• visible：‌指定元素必须可见，‌默认为 False。‌
• hidden：‌指定元素必须隐藏，‌默认为 False。‌
• state：‌可以设置为 visible、‌hidden、‌attached 或 detached，‌用于等待元素达到特定的状态。‌
• timeout：‌设置等待的超时时间，‌以毫秒为单位。‌如果在指定的时间内元素未达到等待的状态，‌则会抛出超时异常。‌

官方定义的函数如下：

    def wait_for_selector(
        self,
        selector: str,
        *,
        state: typing.Optional[
            Literal["attached", "detached", "hidden", "visible"]
        ] = None,
        timeout: typing.Optional[float] = None,
        strict: typing.Optional[bool] = None
    ) -> typing.Optional["ElementHandle"]:
        """ElementHandle.wait_for_selector

        Returns element specified by selector when it satisfies `state` option. Returns `null` if waiting for `hidden` or
        `detached`.

        Wait for the `selector` relative to the element handle to satisfy `state` option (either appear/disappear from dom,
        or become visible/hidden). If at the moment of calling the method `selector` already satisfies the condition, the
        method will return immediately. If the selector doesn't satisfy the condition for the `timeout` milliseconds, the
        function will throw.

        **Usage**

        ```py
        await page.set_content(\"<div><span></span></div>\")
        div = await page.query_selector(\"div\")
        # waiting for the \"span\" selector relative to the div.
        span = await div.wait_for_selector(\"span\", state=\"attached\")
        ```

        ```py
        page.set_content(\"<div><span></span></div>\")
        div = page.query_selector(\"div\")
        # waiting for the \"span\" selector relative to the div.
        span = div.wait_for_selector(\"span\", state=\"attached\")
        ```

        **NOTE** This method does not work across navigations, use `page.wait_for_selector()` instead.

        Parameters
        ----------
        selector : str
            A selector to query for.
        state : Union["attached", "detached", "hidden", "visible", None]
            Defaults to `'visible'`. Can be either:
            - `'attached'` - wait for element to be present in DOM.
            - `'detached'` - wait for element to not be present in DOM.
            - `'visible'` - wait for element to have non-empty bounding box and no `visibility:hidden`. Note that element
              without any content or with `display:none` has an empty bounding box and is not considered visible.
            - `'hidden'` - wait for element to be either detached from DOM, or have an empty bounding box or
              `visibility:hidden`. This is opposite to the `'visible'` option.
        timeout : Union[float, None]
            Maximum time in milliseconds. Defaults to `30000` (30 seconds). Pass `0` to disable timeout. The default value can
            be changed by using the `browser_context.set_default_timeout()` or `page.set_default_timeout()` methods.
        strict : Union[bool, None]
            When true, the call requires selector to resolve to a single element. If given selector resolves to more than one
            element, the call throws an exception.

        Returns
        -------
        Union[ElementHandle, None]
        """

        return mapping.from_impl_nullable(
            self._sync(
                self._impl_obj.wait_for_selector(
                    selector=selector, state=state, timeout=timeout, strict=strict
                )
            )
        )

1.等待元素出现在DOM中

page.wait_for_selector("定位方法", state='attached')

2.等待从DOM中移除

page.wait_for_selector("定位方法", state='detached')

3.等待元素可见

page.wait_for_selector("定位方法", state="visible")

4.等待元素不可见（隐藏）

page.wait_for_selector("定位方法", state='hidden')

如果没有传 state 参数，默认情况下是等待元素可见 visible

page.wait_for_selector("定位方法")

3.2.1等待元素出现和移除

默认情况下，在HTML页面的DOM节点里面是没有这个元素的，通过某些操作（点击【点击关注】按钮），这个元素才出现，如下图所示：

宏哥还是按之前toast的消息那个demo来演示，这里就不写demo的HTML代码，不知道的可以看宏哥之前的文章：传送门

3.2.1.1代码设计

3.2.1.2参考代码

# coding=utf-8🔥

# 1.先设置编码，utf-8可支持中英文，如上，一般放在第一行

# 2.注释：包括记录创建时间，创建人，项目名称。
'''
Created on 2024-07-16
@author: 北京-宏哥
北京宏哥（微信搜索：北京宏哥，关注宏哥，提前解锁更多测试干货！）
Project: 《最新出炉》系列小成篇-Python+Playwright自动化测试-66 - 等待元素至指定状态
'''

# 3.导入模块
from playwright.sync_api import Playwright, sync_playwright, expect

def run(playwright: Playwright) -> None:

    browser = playwright.chromium.launch(headless=False)
    context = browser.new_context()
    page = context.new_page()
    page.goto("E:/Desktop/test/toast.html")
    # 点击 点击关注 按钮
    page.locator("#hongge").click()
    # 等待元素出现在dom
    loc_msg = page.wait_for_selector('//html/body/div', state="attached")
    # 获取元素文本
    print(loc_msg.inner_text())
    page.wait_for_selector('//html/body/div', state="detached")
    print("元素已经从DOM移除")
    page.wait_for_timeout(1000)
    context.close()
    browser.close()

with sync_playwright() as playwright:
    run(playwright)

3.2.1.3运行代码

1.运行代码，右键Run'Test'，就可以看到控制台输出，如下图所示：

2.运行代码后电脑端的浏览器的动作。如下图所示：

3.2.2等待元素显示和隐藏

默认情况下，在HTML页面的元素本身就在DOM里，只是通过某些操作，状态发生改变：隐藏和显示。如下提示语本来就在DOM里，只是默认是隐藏状态。宏哥还在之前的演示demo找到了一个这样的场景，刚好用来演示。

3.2.2.1代码设计

3.2.2.2参考代码

# coding=utf-8🔥

# 1.先设置编码，utf-8可支持中英文，如上，一般放在第一行

# 2.注释：包括记录创建时间，创建人，项目名称。
'''
Created on 2024-07-16
@author: 北京-宏哥
北京宏哥（微信搜索：北京宏哥，关注宏哥，提前解锁更多测试干货！）
Project: 《最新出炉》系列小成篇-Python+Playwright自动化测试-66 - 等待元素至指定状态
'''

# 3.导入模块
from playwright.sync_api import Playwright, sync_playwright, expect

def run(playwright: Playwright) -> None:

    browser = playwright.chromium.launch(headless=False)
    context = browser.new_context()
    page = context.new_page()
    page.goto("https://sahitest.com/demo/visible.htm")
    #点击隐藏按钮
    page.locator("//html/body/form/input[4]").click()
    page.wait_for_selector("#uv", state="hidden")
    print("元素已经隐藏")
    page.wait_for_timeout(1000)
    # 点击显示按钮
    page.locator("//html/body/form/input[5]").click()
    loc_msg = page.wait_for_selector("#uv", state="visible")
    print("元素已经显示")
    # 获取元素文本
    print(loc_msg.inner_text())
    page.wait_for_timeout(1000)
    context.close()
    browser.close()

with sync_playwright() as playwright:
    run(playwright)

3.2.2.3运行代码

1.运行代码，右键Run'Test'，就可以看到控制台输出，如下图所示：

2.运行代码后电脑端的浏览器的动作（注意：using visibility显示和隐藏，可以加长等待时间，看的更清楚）。如下图所示：

3.3 wait_for_element_state()

wait_for_load_state()，等待事件被触发。等待前面按钮触发的事件加载完成，才进行下面的操作。

在Python的Playwright库中，‌wait_for_load_state()方法用于等待页面达到特定的加载状态。‌该方法接受三个参数：‌

• state：‌页面应该达到的加载状态，‌可以是load、‌domcontentloaded或networkidle。‌这些状态分别代表页面的不同加载程度，‌其中load表示页面完全加载，‌domcontentloaded表示文档内容已经加载，‌而networkidle则表示网络几乎无连接，‌即页面加载已完成。‌

• timeout：‌等待的最长时间，‌单位为毫秒。‌默认值为30 * 1000，‌即30秒。‌这个参数用于设置等待操作的最大超时时间，‌以避免程序长时间等待而无法继续执行。‌

• wait_until：‌等待的事件类型，‌可以是load、‌domcontentloaded、‌networkidle0或networkidle2中的一个。‌这个参数用于指定等待的具体事件类型，‌以便更精确地控制等待的条件。‌

通过使用wait_for_load_state()方法，‌可以确保在继续执行后续操作之前，‌页面已经完全加载完成，‌从而避免因页面元素未完全加载而导致的操作失败或错误。

官方定义的函数如下：

    def wait_for_load_state(
        self,
        state: typing.Optional[
            Literal["domcontentloaded", "load", "networkidle"]
        ] = None,
        *,
        timeout: typing.Optional[float] = None
    ) -> None:
        """Page.wait_for_load_state

        Returns when the required load state has been reached.

        This resolves when the page reaches a required load state, `load` by default. The navigation must have been
        committed when this method is called. If current document has already reached the required state, resolves
        immediately.

        **Usage**

        ```py
        await page.get_by_role(\"button\").click() # click triggers navigation.
        await page.wait_for_load_state() # the promise resolves after \"load\" event.
        ```

        ```py
        page.get_by_role(\"button\").click() # click triggers navigation.
        page.wait_for_load_state() # the promise resolves after \"load\" event.
        ```

        ```py
        async with page.expect_popup() as page_info:
            await page.get_by_role(\"button\").click() # click triggers a popup.
        popup = await page_info.value
        # Wait for the \"DOMContentLoaded\" event.
        await popup.wait_for_load_state(\"domcontentloaded\")
        print(await popup.title()) # popup is ready to use.
        ```

        ```py
        with page.expect_popup() as page_info:
            page.get_by_role(\"button\").click() # click triggers a popup.
        popup = page_info.value
        # Wait for the \"DOMContentLoaded\" event.
        popup.wait_for_load_state(\"domcontentloaded\")
        print(popup.title()) # popup is ready to use.
        ```

        Parameters
        ----------
        state : Union["domcontentloaded", "load", "networkidle", None]
            Optional load state to wait for, defaults to `load`. If the state has been already reached while loading current
            document, the method resolves immediately. Can be one of:
            - `'load'` - wait for the `load` event to be fired.
            - `'domcontentloaded'` - wait for the `DOMContentLoaded` event to be fired.
            - `'networkidle'` - **DISCOURAGED** wait until there are no network connections for at least `500` ms. Don't use
              this method for testing, rely on web assertions to assess readiness instead.
        timeout : Union[float, None]
            Maximum operation time in milliseconds, defaults to 30 seconds, pass `0` to disable timeout. The default value can
            be changed by using the `browser_context.set_default_navigation_timeout()`,
            `browser_context.set_default_timeout()`, `page.set_default_navigation_timeout()` or
            `page.set_default_timeout()` methods.
        """

        return mapping.from_maybe_impl(
            self._sync(self._impl_obj.wait_for_load_state(state=state, timeout=timeout))
        )

宏哥在这个网站：https://www.jq22.com/ 找了一个demo，只有加载完成才会出现文字，然后对其进行定位打印文本。

3.3.1代码设计

3.3.2参考代码

# coding=utf-8🔥

# 1.先设置编码，utf-8可支持中英文，如上，一般放在第一行

# 2.注释：包括记录创建时间，创建人，项目名称。
'''
Created on 2024-07-16
@author: 北京-宏哥
北京宏哥（微信搜索：北京宏哥，关注宏哥，提前解锁更多测试干货！）
Project: 《最新出炉》系列小成篇-Python+Playwright自动化测试-66 - 等待元素至指定状态
'''

# 3.导入模块
from playwright.sync_api import Playwright, sync_playwright, expect

def run(playwright: Playwright) -> None:

    browser = playwright.chromium.launch(headless=False)
    context = browser.new_context()
    page = context.new_page()
    page.goto("https://www.jq22.com/demo/jquery-jdt20160820/")
    page.wait_for_load_state()
    print(page.locator('//*[@id="progress_content"]/i[4]/span').inner_text())
    context.close()
    browser.close()

with sync_playwright() as playwright:
    run(playwright)

3.3.3运行代码

1.运行代码，右键Run'Test'，就可以看到控制台输出，如下图所示：

2.运行代码后电脑端的浏览器的动作。如下图所示：

敲黑板！！！1.注意自动化测试的加载的时间不要超过此方法的默认时间，超时就会报错了哈！！！这个网站需要加载40S才会出现文字，如下图所示：

3.3.4代码设计

3.3.5参考代码

# coding=utf-8🔥

# 1.先设置编码，utf-8可支持中英文，如上，一般放在第一行

# 2.注释：包括记录创建时间，创建人，项目名称。
'''
Created on 2024-07-16
@author: 北京-宏哥
北京宏哥（微信搜索：北京宏哥，关注宏哥，提前解锁更多测试干货！）
Project: 《最新出炉》系列小成篇-Python+Playwright自动化测试-66 - 等待元素至指定状态
'''

# 3.导入模块
from playwright.sync_api import Playwright, sync_playwright, expect

def run(playwright: Playwright) -> None:

    browser = playwright.chromium.launch(headless=False)
    context = browser.new_context()
    page = context.new_page()
    page.goto("https://sahitest.com/demo/php/delayedLoadInner.php")

    page.wait_for_load_state()

    print(page.locator("//html/body/div").inner_text())
    print(page.locator("//html/body/span").inner_text())
    context.close()
    browser.close()

with sync_playwright() as playwright:
    run(playwright)

3.3.6运行代码

1.运行代码，右键Run'Test'，就可以看到控制台输出（.运行代码控制台报错，因为加载这个页面需要40s，而此方法默认30000ms=30s，超时报错），如下图所示：

2.运行代码后电脑端的浏览器的动作。如下图所示：

4.小结

4.1wait_for() 和 wait_for_selector()使用区别

wait_for() 方法 和 wait_for_selector()使用区别：

page.locator('定位元素').wait_for() 返回的是None，后面不能继续操作元素

page.wait_for_selector("定位方法") 返回的是locator 对象，后面可以继续操作元素

好了，今天时间也不早了，宏哥就讲解和分享到这里，感谢您耐心的阅读，希望对您有所帮助。