PYTHON 幫助

使用 Tenacity 在 Python 中重试功能

Name: IronPDF
Brand: Iron Software
Availability: InStock
Rating: 4.87 (307 reviews)

更新日期:6月 22, 2025

在以Python程式語言開發強大且具彈性的程式時，通常需要優雅地處理臨時錯誤，特別是在使用外部服務或網路操作時。這就是強大的Python通用重試庫Tenacity的用武之地。開發人員可以藉由將Tenacity與IronPDF結合，提升其PDF生成操作的可靠性和魯棒性，IronPDF是一個功能豐富的框架，用於在Python應用程式中創建PDF文件。

Tenacity提供了一個可調整和可自定義的結構，用於重試因暫時性問題（如網路故障、超時或服務中斷）而可能失敗或引發异常的任務。Tenacity通過其用戶友好的API和廣泛的功能集簡化了重試邏輯的開發，讓開發者可以專注於創建可靠的系統，而無需擔心短暫的失敗。

在本文中，我們將探討將Tenacity庫與IronPDF結合的優勢，提供實用的範例，並給出如何在Python應用程式中創建可靠的PDF生成過程的建議。開發者可以藉由將Tenacity的強大功能與IronPDF結合，在提供高質量PDF文件給消費者的同時，提升其應用的穩定性和可靠性。

基於裝飾器的重試

Tenacity使程式員可以使用Python裝飾器，為函數或方法添加重試邏輯。因此可以很容易地為特定操作添加重試行為，而不需要更改原始代碼。

可調整的重試計劃

Tenacity提供多個可調整的參數來指定重試計劃。最大重試次數、重試之間的間隔以及重試應發生的條件都可以由開發者自定義。

指數退避

Tenacity支持指數退避，一種流行的當前重試調用技術，其中重試之間的間隔隨每次嘗試的次數指數增長。通過這樣做，您可以避免在流量或擁塞較多時向目標服務發出過多請求。

抖動和隨機性

Tenacity提供引入抖動和隨機性的選項，以防止同步化問題和轟雷群效應。這減少了多個客戶端同時重試的可能性，通過將重試努力分散在時間上。

重試條件和异异常

根據操作的返回值或任何引發的异常，開發者可以創建獨特的重試條件。這使得可以精確調控何時和在何種情況下應進行重試。

超時和截止日期

Tenacity促進了常規操作超時和截止日期的創建，以確保重試嘗試不會無限期進行，並且如果操作超過預定的閾值，則最終會中止。

與流行的Python框架集成

Tenacity容易與Flask、Django和Celery等框架互動。這使得開發者可以輕鬆地為後台操作、網頁端點或系統的任何其他部分添加重試邏輯。

創建和配置Tenacity

指數退避

from tenacity import retry, wait_exponential

# Decorate the function with a retry mechanism
@retry(wait=wait_exponential(multiplier=1, min=1, max=10))
def my_function():
    # Your code logic here
    pass

# Explanation:
# - `multiplier`: Used to increase the interval between retries.
# - `min`: Minimum wait time in seconds between retries.
# - `max`: Maximum wait time allowed between retries.

from tenacity import retry, wait_exponential

# Decorate the function with a retry mechanism
@retry(wait=wait_exponential(multiplier=1, min=1, max=10))
def my_function():
    # Your code logic here
    pass

# Explanation:
# - `multiplier`: Used to increase the interval between retries.
# - `min`: Minimum wait time in seconds between retries.
# - `max`: Maximum wait time allowed between retries.

PYTHON

隨機抖動

from tenacity import retry, wait_random

@retry(wait=wait_random(min=1, max=10))
def my_function():
    # Your code logic here
    pass

# Explanation:
# - `min`: Minimum random wait time in seconds between retries.
# - `max`: Maximum random wait time in seconds between retries.

from tenacity import retry, wait_random

@retry(wait=wait_random(min=1, max=10))
def my_function():
    # Your code logic here
    pass

# Explanation:
# - `min`: Minimum random wait time in seconds between retries.
# - `max`: Maximum random wait time in seconds between retries.

PYTHON

自定義重試條件

自定義例外重試

from tenacity import retry, retry_if_exception_type

# Retry on specific exceptions like ConnectionError
@retry(retry=retry_if_exception_type(ConnectionError))
def my_function():
    # Your code logic here
    pass

# Explanation:
# Retry only if a ConnectionError exception is raised during the function execution.

from tenacity import retry, retry_if_exception_type

# Retry on specific exceptions like ConnectionError
@retry(retry=retry_if_exception_type(ConnectionError))
def my_function():
    # Your code logic here
    pass

# Explanation:
# Retry only if a ConnectionError exception is raised during the function execution.

PYTHON

根據返回值重試

from tenacity import retry, retry_if_result

@retry(retry=retry_if_result(lambda result: result is None))
def my_function():
    # Your code logic here
    return some_result

# Explanation:
# Retry if the function result is `None`.

from tenacity import retry, retry_if_result

@retry(retry=retry_if_result(lambda result: result is None))
def my_function():
    # Your code logic here
    return some_result

# Explanation:
# Retry if the function result is `None`.

PYTHON

停止條件

from tenacity import retry, stop_after_delay

@retry(stop=stop_after_delay(30))
def my_function():
    # Your code logic here
    pass

# Explanation:
# Stop retrying after 30 seconds have elapsed since the first attempt.

from tenacity import retry, stop_after_delay

@retry(stop=stop_after_delay(30))
def my_function():
    # Your code logic here
    pass

# Explanation:
# Stop retrying after 30 seconds have elapsed since the first attempt.

PYTHON

重試回調

from tenacity import retry, after_log
import logging

logger = logging.getLogger(__name__)

@retry(after=after_log(logger, logging.DEBUG))
def my_function():
    # Your code logic here
    pass

# Explanation:
# Use a logger to log details of each retry attempt at the DEBUG level.

from tenacity import retry, after_log
import logging

logger = logging.getLogger(__name__)

@retry(after=after_log(logger, logging.DEBUG))
def my_function():
    # Your code logic here
    pass

# Explanation:
# Use a logger to log details of each retry attempt at the DEBUG level.

PYTHON

開始使用

什麼是 IronPDF？

我們可以通過流行的工具包IronPDF在程序內創建、編輯和渲染PDF文檔。以多種方式處理PDF：您可以將HTML頁面轉換為PDF，將文本、圖像和形狀添加到已存在的頁面中，並從已存在的頁面中提取文本和圖像。甚至可以從HTML內容、圖像或原始數據創建新的PDF頁面。

IronPDF極其易於使用，這是其主要優勢之一。 Python用戶友好的API和詳細的文檔使得開發者可以輕鬆地從他們的項目中開始創建PDF。 IronPDF還具有兩個更多的特點：速度和效率，讓開發人員快速創建高質量的PDF文檔。

IronPDF的一些優勢：

將圖像、原始數據和HTML轉換為PDF。
從PDF文件中移除圖像和文本。
向PDF文件中添加頁眉、頁腳和水印。
用密碼和加密保護PDF文件。
可以進行電子簽名和填寫表單。

安裝庫

在Python應用程式中使用Tenacity和IronPDF一起的第一步是安裝所需的依賴項並將兩個庫集成到您的PDF生成工作流程中。

pip install tenacity
pip install ironpdf

pip install tenacity
pip install ironpdf

SHELL

在您的Python腳本中，從Tenacity和IronPDF中導入所需的模塊：

from tenacity import retry, stop_after_attempt, wait_fixed
from IronPdf import IronPdf

# Set up retry behavior on the PDF generating function
@retry(
    stop=stop_after_attempt(3),   # Stop retrying after 3 attempts
    wait=wait_fixed(2)            # Wait 2 seconds between retry attempts
)
def generate_pdf(html_content):
    iron_pdf = IronPdf()
    # Render the HTML content as a PDF
    iron_pdf.render_html_as_pdf(html_content)
    # Save the generated PDF to a file
    iron_pdf.save_as_pdf("output.pdf")

# Explanation:
# - `@retry(stop=stop_after_attempt(3))`: Stop after 3 failed attempts.
# - `wait_fixed(2)`: Wait 2 seconds before each retry attempt.

from tenacity import retry, stop_after_attempt, wait_fixed
from IronPdf import IronPdf

# Set up retry behavior on the PDF generating function
@retry(
    stop=stop_after_attempt(3),   # Stop retrying after 3 attempts
    wait=wait_fixed(2)            # Wait 2 seconds between retry attempts
)
def generate_pdf(html_content):
    iron_pdf = IronPdf()
    # Render the HTML content as a PDF
    iron_pdf.render_html_as_pdf(html_content)
    # Save the generated PDF to a file
    iron_pdf.save_as_pdf("output.pdf")

# Explanation:
# - `@retry(stop=stop_after_attempt(3))`: Stop after 3 failed attempts.
# - `wait_fixed(2)`: Wait 2 seconds before each retry attempt.

PYTHON

調用您的創建PDF文檔的功能，並將HTML文本傳遞給它。如果出現异常，Tenacity將根據預設的重試參數自動重試該函數。

try:
    html_content = "<html><body><h1>Hello, IronPDF!</h1></body></html>"
    generate_pdf(html_content)
    print("PDF generated successfully")
except Exception as e:
    print("Failed to generate PDF:", e)

# Explanation:
# Attempt to generate a PDF and handle any exceptions that might occur during the process.

try:
    html_content = "<html><body><h1>Hello, IronPDF!</h1></body></html>"
    generate_pdf(html_content)
    print("PDF generated successfully")
except Exception as e:
    print("Failed to generate PDF:", e)

# Explanation:
# Attempt to generate a PDF and handle any exceptions that might occur during the process.

PYTHON

通過修改因素，比如重試的次數、重試條件和等待條件、重試之間的間隔及重試應發生的情況，您可以進一步調整重試行為。 Tenacity包括不同的重試方法和重試和等待條件策略，您可以使用它們根據您的需求調整重試行為。