4 ms·

Now you have me wondering how difficult it would be to have a class that takes a string and parses through globals to find the context it was called from. maybe

Now you have me wondering how difficult it would be to have a class that takes a string and parses through globals to find the context it was called from. maybe causing an exception and abusing a traceback? or maybe we just find our own objectid.... gahh I have to try it now, but I'm setting a timer.

dec0dedab0de 2y ago
It was easier than I thought, but also took longer than I wanted to. turns out the inspect module provides what you need to pull it off. This dummy example splits a string that it was given, then if one of those values is in the callers context it saves those in self.context, and has an output function to assemble it all together. Obviously this example is not very useful, but it shows how a library could do this as a class or function without the user having to pass in locals(). import inspect class MyXString: """ will split on whitespace and replace any string that is a variable name with the result of str(variable)""" def __init__(self, string): self.string = string caller_locals = inspect.currentframe().f_back.f_locals self.context = {} for key in set(string.split()): if key in caller_locals: self.context[key] = caller_locals[key] def output(self): output = self.string for k,v in self.context.items(): output = output.replace(k,str(v)) return output
- nhumrich 2y ago
  This looks like a performance nightmare, and would likely never have IDE integration. So I guess I was wrong. It could be a library. But will be much better supported officially.
zephyrfalcon 2y ago
You don't have to go through all the globals, you just have to get the caller's namespace, which is fairly simple. See e.g. https://stackoverflow.com/a/6618825/27426 https://stackoverflow.com/a/6618825/27426 For this reason, I think it's not true that this absolutely had to be a language feature rather than a library. A template class written in pure Python could have done the same lookup in its __init__.
- dec0dedab0de 2y ago
  That is exactly what I ended up doing: https://news.ycombinator.com/item?id=43752889 https://news.ycombinator.com/item?id=43752889

dec0dedab0de 2y ago

It was easier than I thought, but also took longer than I wanted to. turns out the inspect module provides what you need to pull it off. This dummy example splits a string that it was given, then if one of those values is in the callers context it saves those in self.context, and has an output function to assemble it all together. Obviously this example is not very useful, but it shows how a library could do this as a class or function without the user having to pass in locals(). import inspect class MyXString: """ will split on whitespace and replace any string that is a variable name with the result of str(variable)""" def __init__(self, string): self.string = string caller_locals = inspect.currentframe().f_back.f_locals self.context = {} for key in set(string.split()): if key in caller_locals: self.context[key] = caller_locals[key] def output(self): output = self.string for k,v in self.context.items(): output = output.replace(k,str(v)) return output

nhumrich 2y ago
This looks like a performance nightmare, and would likely never have IDE integration. So I guess I was wrong. It could be a library. But will be much better supported officially.

zephyrfalcon 2y ago

You don't have to go through all the globals, you just have to get the caller's namespace, which is fairly simple. See e.g. https://stackoverflow.com/a/6618825/27426 https://stackoverflow.com/a/6618825/27426 For this reason, I think it's not true that this absolutely had to be a language feature rather than a library. A template class written in pure Python could have done the same lookup in its __init__.

dec0dedab0de 2y ago
That is exactly what I ended up doing: https://news.ycombinator.com/item?id=43752889 https://news.ycombinator.com/item?id=43752889