I once was in the position of becoming pr approver[1] for a team of outsourced python programmers who were under some pretty extreme deadline pressure. Anyway one day a PR comes in and I can’t help but notice it was doing a string eval.
Weird. You almost never need to do string eval in python, and whenever there is something where you think you need eval there is a better and safer way to achieve the same result.
Also, I was bending my brain but I couldn’t really figure out what this eval was for until I wrote out some scratch code myself to figure it out.
Turns out this 5 lines or so was constructing a string to do dict lookup and then evalling that. So say you have a dict d = {‘foo’: ‘bar’} and you have a variable i=foo and want to look up d[i], instead of just doing that it was doing something like
eval(‘d[‘+i+’]’)
Just no.
So I rejected the change and they came back with “but we’ve always done it that way”. I grep the codebase and yes. There were about 200+ uses of eval, all of which were constructing a string to look something up in a dictionary and then evaling the result. Some person who clearly didn’t program in python had found this twisted way to look things up in a dictionary and then this team had dutifully copied and pasted it throughout the codebase.
[1] ie I wasn’t there from the start of the project
Weird. You almost never need to do string eval in python, and whenever there is something where you think you need eval there is a better and safer way to achieve the same result.
Also, I was bending my brain but I couldn’t really figure out what this eval was for until I wrote out some scratch code myself to figure it out.
Turns out this 5 lines or so was constructing a string to do dict lookup and then evalling that. So say you have a dict d = {‘foo’: ‘bar’} and you have a variable i=foo and want to look up d[i], instead of just doing that it was doing something like
Just no.So I rejected the change and they came back with “but we’ve always done it that way”. I grep the codebase and yes. There were about 200+ uses of eval, all of which were constructing a string to look something up in a dictionary and then evaling the result. Some person who clearly didn’t program in python had found this twisted way to look things up in a dictionary and then this team had dutifully copied and pasted it throughout the codebase.
[1] ie I wasn’t there from the start of the project