[Python-ideas] Show deprecation warnings in the interactive interpreter

[Terry Reedy]

On 2/25/2015 4:35 PM, Nick Coghlan wrote:

> Setting the action to "always" and filtering on the main module should
> do the trick:
>
> >>> import warnings
> >>> warnings.filterwarnings("always", module="__main__")

Changing interactive-mode python is irrelevant to gui environments 
running on batch-mode python, except for adding another requirement for 
simulating interactive python and its command prompt.  Idle starts 
idlelib/PyShell.py in one process (the Idle process) and (in default 
mode) idlelib/run.py in a second process (the User process) and makes a 
bidirectional connection.  The Idle process compiles user code with 
compile(codestring, ...) and sends the code object to the User process, 
which executes it with exec(usercode, namespace).

Both processes already import warnings.  If I add the line above to 
run.py, I get

 >>> warnings.warn("Deprecated", DeprecationWarning)

Warning (from warnings module):
   File "__main__", line 1
DeprecationWarning: Deprecated

(on stderr) instead of nothing.  I presume this should be sufficient for 
runtime warnings, but are there any raised during compilation (like 
SyntaxWarnings, or Py3kWarnings in 2.7)?  I see nothing in the compile() 
doc about turning warnings on or off.

-- 
Terry Jan Reedy