@contextlib.contextmanager
时间: 2023-04-30 22:06:26 浏览: 67
'@contextlib.contextmanager' 是一个装饰器,用于创建上下文管理器。使用 with 语句来管理代码块,这样可以确保代码块在执行完后会被自动清理。@contextlib.contextmanager 装饰器可以让我们更轻松地创建自定义的上下文管理器。
相关问题
@contextmanager
The @contextmanager decorator in Python allows you to create a context manager using a generator function. A context manager is a class or function that is used to manage resources, such as opening and closing a file or acquiring and releasing a lock. The @contextmanager decorator provides a simple and concise way to create a context manager without having to define a class.
The decorator takes a generator function as input and returns a context manager. The generator function must yield exactly once to indicate the beginning of the context and again at the end to indicate the end of the context. Any code inside the with statement will be executed within the context.
Here is an example of a context manager created using the @contextmanager decorator:
```python
from contextlib import contextmanager
@contextmanager
def open_file(file_path):
file = open(file_path, 'w')
try:
yield file
finally:
file.close()
with open_file('test.txt') as f:
f.write('Hello, world!')
```
In this example, the open_file() function is decorated with @contextmanager. The function opens a file for writing and yields the file object. The try-finally block ensures that the file is closed properly when the context is exited.
The with statement is used to create a context in which the file is opened and used to write a string to the file. When the with block is exited, the file is closed automatically.
The @contextmanager decorator is a useful tool for creating context managers in a concise and readable manner.
File "C:\Users\HUAWEI\.conda\envs\pytorch1\lib\contextlib.py", line 75, in inner return func(*args, **kwds)
这是Python标准库中的contextlib模块的源代码中的一行。在这行代码中,定义了一个名为inner的函数,并且使用了装饰器(@contextmanager)来将其转换为上下文管理器。上下文管理器用于管理资源的获取和释放,确保在使用完资源后能够正确地进行清理操作。
具体来说,这行代码中的inner函数是一个生成器函数,它使用yield语句将控制权交给with语句块外部的代码,并在with语句块执行完毕后再次恢复执行。这样可以在进入和退出with语句块时执行一些特定的操作。
如果你有具体的问题或者需要更详细的解释,请告诉我。
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