read-only mode

[maxhutch]

I use chests to distribute data. In most cases, the data consumer either doesn't want to change the contents of the chest or doesn't even have the file permissions to. chests write the .keys to disk at close, even if they haven't changed. __delitem__ and __setitem__ both delete files even before a flush, so it might be nice to protect them from programmer errors.

Does this seem useful enough to belong in chest itself, or should I implement this on my end in a subclass or the likes?

[mrocklin]

Seems useful to me

[shoyer]

You might find the Frozen utility I wrote for xray useful for this:
https://github.com/xray/xray/blob/d704524a030aef7e2029ec43d19099143b72f653/xray/core/utils.py#L233

You could use it like Frozen(Chest(...)).

[maxhutch]

That avoids __delitem__ and __setitem__, but still has the problem of writings .keys on __del__.

I'll open a PR shortly.