Earlier quoted context omitted.
Many modern languages have a convenient solution for those cases as well: Python has the "with" statement combined with context managers; C# has the "using" block with the "IDisposable" interface that does essentially the same thing; even Java recently got its corresponding "try-with-resources". Before those were introduced we had try/finally which works equally well but is slightly more verbose.
Yes, you can do this with try/finally. But if you have an object that has an open file as a member, then you open the file in the constructor, and then use the open file in the member methods, and then... what? You may have a scope that you are exiting where that object becomes irrelevant, but it may be several layers away. Having to close that object's handle in a finally in that scope seems likely to be forgotten a…
If an object has resources to dispose of (such as an open file), it should implement (to use C# as an example – it looks similar in Python and Java) the IDisposable interface, which allows you to do either:
MyFileWrapperObject obj = ...;
try {
foo();
bar();
...
}
finally {
obj.Dispose();
}
using (MyFileWrapperObject obj = ...) {
foo();
bar();
...
}
with open("something.json") as f:
data = json.load(f)