Have you considered using a templating library like Jinja2 or Mako? That's my
first thought whenever I want something that's too complicated for
`str.format()`. In addition to handling default values, these libraries would
also give you the ability to encode some simple logic in your files, which may
be useful.
-Kale
On 4/1/22 02:26, brian.patrick.mcc...@gmail.com wrote:
> One way that I like to create templates for config files is to write the
> config file in a way that can be used with `str.format` if I read in the
> entire config file as a string before re-saving it or sending it somewhere.*
> The config file contains a half dozen or dozen variables. Another several
> dozen variables are pretty much permanent. This approach works for me in the
> sense that batch submits over several combinations of variables is just a few
> lines of code, and when I revisit a job after quite some time, the curly
> braces in the config file template remind me what settings (might) require my
> attention. The problem lies in what to do about defaults. Including a
> formatted variable in the template file requires that the variable be
> included in my call to `format` otherwise I'll get a `KeyError`. For my part,
> I can work around this by including a companion '.py' file that includes a
> `dict` of default values. What I pine for is the ability to discard this
> extra '.py' file, and its WYS
> INWYG heresy by enabling a way to enable defaults in the processing of
> formatted strings. One such way would be to modify the format string spec. I
> am not sure how this might be done, so I cannot make a smart proposal on that
> one. Another way, although it might not be the most popular, is to allow for
> inline exception handling of the sort proposed in PEP 463.
>
> To me, the following does not look so bad:
> Config file:
> ```
> ...
> BAUD: {baud except 9600}
> ...
> ```
>
> Template updating code snippets:
> ```
> with open('config.yaml', 'r') as f:
> txt = f.read()
> options = {'baud': 19200}
> new_txt1 = txt.format(options) # BAUD: 19200 is now in new_txt1
> options = {}
> new_txt2 = txt.format(options) # BAUD: 9600 is now in new_txt2
> ```
>
>
> Curious to know anyone's thoughts on the subject, particularly anyone else
> who is in the habit of hastily writing config files. Apologies if bringing up
> a rejected PEP on my first thread causes any irritation, but I swear I would
> not have done it if string formatting weren't so useful. I thank you for my
> cookie and now I would like some milk.
>
> * - I'm aware that there can be security risks in this approach, but I am
> working in a walled off system (not public) where it is unlikely that I or
> anyone else can do much damage even if we wanted to.
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