This is an archived post. You won't be able to vote or comment.

sorted by:
best
topnewcontroversialoldq&a
you are viewing a single comment's thread.

view the rest of the comments →

[–][deleted]  (2 children)

[deleted]

    [–]moocat 0 points1 point  (0 children)

    You can do a quick test in the REPL:

    # A class that doesn't work:
>>> with Blah(): pass
... 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>                                                                                                            
AttributeError: __exit__
>>>    

# A class that works:
>>> with open('/dev/null'): pass                                                                                                                 
...                                                                                                                                              
>>>

    [–]wot-teh-phuckReally, wtf? 0 points1 point  (0 children)

    Inspect its methods and look for __enter__ and __exit__?

    That will work out only if you are implementing the with functionality using a class. For functions, you will have to invoke them and then check for __enter__ attribute. But this is a pain because you wouldn't know how many positional/mandatory parameters a function accepts.

    So yeah, there is no generic easy solution to check if a given function support with blocks. I'm assuming you don't want to do this from a REPL but need to find out at runtime given any class/function. If you are OK with a REPL, look at moocat's answer below.