Difference between running code in shell and from file

Question

I'm new to the csv module (and Python in general). I was running some test code to write a CSV file and I realized that it functions when I run it in the shell but not when I run it from a file in IDLE. When I try the latter, it tells me that "open" is invalid syntax. What's going on here?

import csv
with open('csvtest.csv', 'w') as f:
    writer = csv.writer(f)
    writer.writerow('test1', 'test2', 'test3')

Answer 1

Quoth the documentation

New in version 2.5.

The with statement is used to wrap the execution of a block with methods defined by a context manager (see section With Statement Context Managers).

Your IDLE is probably running Python 2.4 or earlier.