使用 context manager

Python 函式寫作

Shayne Miel

Software Architect @ Duo Security

什麼是 context manager？

Context manager：

建立情境
執行你的程式碼
移除情境

外燴派對

空房間

外燴派對

外燴佈置

外燴派對

派對中

外燴派對

外燴佈置

外燴派對

空房間

把外燴派對當情境類比

Context manager：

建立情境
執行你的程式碼
移除情境

外燴團隊：

佈置餐桌與餐飲
讓你和朋友盡情開趴
收拾並撤走餐桌

真實範例

with open('my_file.txt') as my_file:
  text = my_file.read()
  length = len(text)

print('The file is {} characters long'.format(length))

open() 做了三件事：

開啟檔案以建立情境
讓你在該檔案上執行任意程式碼
關閉檔案以移除情境

使用 context manager

with

使用 context manager

with <context-manager>()

使用 context manager

with <context-manager>(<args>)

使用 context manager

with <context-manager>(<args>):

使用 context manager

with <context-manager>(<args>):
  # Run your code here
  # This code is running "inside the context"

使用 context manager

with <context-manager>(<args>):
  # Run your code here
  # This code is running "inside the context"

# This code runs after the context is removed

使用 context manager

with <context-manager>(<args>) as <variable-name>:
  # Run your code here
  # This code is running "inside the context"

# This code runs after the context is removed

with open('my_file.txt') as my_file:
  text = my_file.read()
  length = len(text)

print('The file is {} characters long'.format(length))

一起來練習吧！

Python 函式寫作