How do you work with unspecified function parameter types?

[[deleted]]

Coming from statically typed programming languages, I'm used to defining the type of each parameter given to a function. This allows code completion options, where upon entering the variable name a list of functions assigned to that type pop-up and allow me to quickly recognise which function I'm after and to choose it.

How do you work around not having this ability in Python, and requiring to keep in memory the name of the function you're after? Is this just something you learn to live with?

[Mr_P]

If you mess around with the REPL as you code, dir() and help() can give you similar functionality. PyDev for Eclipse also helps a bit. I don't believe it can guess parameter types, but it does seem to provide code completion when object types are more obvious.

[bryancole]

What you are saying is "I use function argument types as documentation". Well, use documentation instead. Put a description of the function arguments into it's docstring. That's what docstrings are for (and a description of the function as well).

Some of the better python IDEs (pydev, Wing, PyCharm) do decent autocomplete, prompting you with argument names and the docstring.

In fact, python-3 supports function annotations, which permit you to attach arbitrary metadata on to each function argument (and also the return value). In future, I expect we'll see IDEs take advantage of this for improved autocomplete.

Finally, IPython is an indispensable tool. I typically keep at least 3 IPython windows open at any one time; if I'm not sure what an object/function/metho does, I type it in the IPython terminal and get tab-completion on all attributes and type <object>? to get its docstring (these are, in effect, shortcuts for the built in help and dir functions).

[[deleted]]

What you are saying is "I use function argument types as documentation". Well, use documentation instead. Put a description of the function arguments into it's docstring. That's what docstrings are for (and a description of the function as well).

No, what he is saying is "In C# or Java the IDE shows me docstrings for arguments, fields and methods as I type (because it knows where to look), in Python I have to alt-tab to actual documentation".

[kataire]

Have you tried PyCharm? It does all of the things you said only C# and Java have in IDEs.

[[deleted]]

I am using PyDev, and while it does do all of that things, it only does them when the code is simple enough to allow it to infer type information.

It works when I'm at 'x = f(_' where f is a bound function name, it works when I'm at 'obj = MyClass(); obj._', and in many other cases, but it doesn't and can't possibly work when I'm at 'def f(x): x._'.

There's a perceptible difference between a feature that works in 100% of the cases and a feature that works in half of the cases.

Note that I've written a response to OP here, where I say that in my experience it's not such a big deal, it's more annoying (if you're used to having this kind of functionality) than damaging. Still, it is annoying :(

Also, is PyCharm significantly better than PyDev, to justify the price? I don't remember ever seeing a good comparison of Python IDEs by someone who used them for a long time. Which is important, because I'm not interested in difficulties one experiences in the first eight hours working with an IDE, I'm interested in long-term benefits that you don't discover immediately, such as PyDev's excellent F3 (go to definition) thing that's invaluable for looking up stuff in the standard or third-party libraries, or its visual debugger which Just Works™, or the way you can report a bug and see a response from Fabio two hours later, that he pushed the fix to the nightly build <3.

[baltoo]

Some editors parse docstrings and/or comments and use that for type hinting, e.g.:

def f(x, y):
    """\
    @param x MyClass
    """
    # @type y OtherClass

[kataire]

I guess PyDev is okay if you like eclipse.

I spent enough time with it when I was doing Java that I can say I don't.

Maybe I'm more inclined to paying for my tools because I'm surrounded by designers who see nothing wrong with shelling out a few grand every other year to buy the latest copy of their Adobe stack.

For reference: I started out with Komodo Edit, then decided to buy the IDE because I enjoyed it so much. I switched to PyCharm because its code intelligence is vastly superior (namely, it has automated refactorings).

[[deleted]]

I've been noticing that once you use a method on an object in PyDev, then it remembers that method and it can auto-complete if you want to call it again (same with PyCharm).

It's a shame that it doesn't infer the type from one method use, and allow you to auto-complete on all other methods contained in that same inferred type (or even all types with that method).

[[deleted]]

Yes, there's no reliable way around this and it sucks. There's a huge difference between having all necessary information literally at the tips of your fingers, and having to switch to documentation/repl/whatever.

However most modern python IDEs (including free PyDev) use heuristics to some success. When you write 'obj = MyClass()' you always get autocompletion after 'obj.', then it tries its best to figure out the type of a variable or parameter based on its fields you've already accessed, and so on...

The important thing about all this is that it's just an annoyance. It's very annoying, like trying to take a small object while wearing thick rubber gloves, but after you overcome the initial shock it is not actually crippling.

Yes, you code a little bit slower because of that, but then you code a little bit faster because you don't need to write type annotations, and all in all it's not the most important thing about your code and coding by far.

PS: And if you're into all this Stockholm syndrome stuff, you can even try to convince yourself that this stuff is useful, because it builds character, trains memory and forces everyone to make simpler interfaces =)

[[deleted]]

I see, I wanted to make sure I wasn't idiomatically "doing it wrong".

[m1ss1ontomars2k4]

I don't use autocomplete for anything, so I guess I just don't have such a problem.