What is the python “with” statement designed for?

Question

I came across the Python with statement for the first time today. I\'ve been using Python lightly for several months and didn\'t even know of its existence! G

Answer 1

An example of an antipattern might be to use the with inside a loop when it would be more efficient to have the with outside the loop

for example

for row in lines:
    with open("outfile","a") as f:
        f.write(row)

vs

with open("outfile","a") as f:
    for row in lines:
        f.write(row)

The first way is opening and closing the file for each row which may cause performance problems compared to the second way with opens and closes the file just once.