The with statement applies to instances having 2 methods: "__enter__" and "__exit__". When the with statement is encountered, the instance's __enter__ method is called and its return value is used for the 'as' part of the statement. When the block exits, the instance's __exit__ method is called to perform cleanup action. In the case of a file object, the __exit__ method closes the file.
return "block value"
def __exit__(self, *args):
with A() as value:
my output -->
An alternative to writing a class to create such 'context' instances is to write a function with a single "yield" statement and use the contextmanager decorator like this
from contextlib import contextmanager
yield "block value"
with B() as value:
""" my output -->
As a more useful example, here is a context which executes a block of statement in a given directory and comes back to the initial directory at the end of the block
old = os.getcwd()
yield # this is where the code in the "with" block will be executed
i am using visual studio 2015 and trying to export data which i am importing through excel by the user selected Excel file. Now the importing part has been successfully completed i am using OLEDB Connection but Stuck in exporting the same data to a new Excel file. tried ...
I am creating a program that when you print an author, you must show all the information of all the books that the author has written. Add a new attribute in the Author class that will be "BooksWriting: List (Book)".
I am currently creating a simulation of a pizza ordering system in object oriented program. I have some question. the instruction and guideline is long but I will try and cut it down a lot. the instruction is to create a program that simulate a pizza restaurant using ...