Using "with" statement for CSV files in Python
Is it possible to use the with statement directly with CSV files? It seems natural to be able to do something like this:
import csv
with csv.reader(open("myfile.csv")) as reader:
# do things with reader
But csv.reader doesn't provide the __enter__ and __exit__ methods, so this doesn't work. I can however do it in two steps:
import csv
with open("myfile.csv") as f:
reader = csv.reader(f)
# do things with reader
Is this second way the ideal way to do it? Why wouldn't they make csv.reader directly compatible with the with statement?
Answer
The primary use of with statement is an exception-safe cleanup of an object used in the statement. with makes sure that files are closed, locks are released, contexts are restored, etc.
Does csv.reader have things to cleanup in case of exception?
I'd go with:
with open("myfile.csv") as f:
for row in csv.reader(f):
# process row
You don't need to submit the patch to use csv.reader and with statement together.
import contextlib
Help on function contextmanager in module contextlib:
contextmanager(func)
@contextmanager decorator.
Typical usage:
@contextmanager
def some_generator(<arguments>):
<setup>
try:
yield <value>
finally:
<cleanup>
This makes this:
with some_generator(<arguments>) as <variable>:
<body>
equivalent to this:
<setup>
try:
<variable> = <value>
<body>
finally:
<cleanup>
Here's a concrete example how I've used it: curses_screen.