Question

What is the python keyword "with" used for?

Example from: http://docs.python.org/tutorial/inputoutput.html

>>> with open('/tmp/workfile', 'r') as f:
... read_data = f.read()
>>> f.closed
True

Answer 1

Explanation from the Preshing on Programming blog:

It’s handy when you have two related operations which you’d like to execute as a pair, with a block of code in between. The classic example is opening a file, manipulating the file, then closing it:

with open('output.txt', 'w') as f:
f.write('Hi there!')

The above with statement will automatically close the file after the nested block of code. (Continue reading to see exactly how the close occurs.) The advantage of using a with statement is that it is guaranteed to close the file no matter how the nested block exits. If an exception occurs before the end of the block, it will close the file before the exception is caught by an outer exception handler. If the nested block were to contain a return statement, or a continue or break statement, the with statement would automatically close the file in those cases, too.

Answer 2

Please visit this site to know abt "with" keyword: http://preshing.com/20110920/the-python-with-statement-by-example/

Answer 3

The with statement in Python simplifies exception handling by encapsulating common preparation and clean-up tasks in so-called context managers. This allows common try..except..finally usage patterns to be encapsulated for convenient reuse and reduce the amount of code you need to write for handling different kinds of exceptions. The with statement creates resources within a block . You write your code using the resources within the block. When the block exits the resources are cleanly released regardless of the outcome of the code in the block (that is whether the block exits normally or because of an exception). More on...Python with statement

Comments

Hi Rahul, thanks for explaining it in-detail. Can you also share some examples here?