Explicitly declaring a variable type in Python

Question

I use pyscripter for coding, it supports auto-completion. So, when I say:

a = []
a.

It gives me all the list functions. similarly with strings I do b=''.

But for the file type, I have to use file. and choose the function and write its arguments and then replace file with the variable name.

Is there a way to declare a variable type explicitly in Python, so that my IDE can be more useful?

Writing bad Python code just to please an IDE doesn't sound like such a great idea to me... — Tim Pietzcker
– Tim Pietzcker, Commented Oct 28, 2010 at 10:08
once you've used a.your_attribute in your code, pyDev-eclipse will keep showing that attribute after pressing . in list with CTRL + SPACE, with its intelligence !!! — shahjapan
– shahjapan, Commented Oct 28, 2010 at 10:11
If you have to make your IDE absolutely useful, you will have to morph python into java .. including specifying the type explicitly. — pyfunc
– pyfunc, Commented Oct 28, 2010 at 10:43
I'm currently switching from C#/Java to Python and the dynamic types seem to create a lot more problems than they solve. They just feel messy and a step backwards. — Damien
– Damien, Commented Jan 16, 2013 at 23:26
Most decent Python IDEs automatically show possible methods on an object when you type obj. : Eclipse, spyder, Wing, Canopy... — smci
– smci, Commented Jun 21, 2013 at 22:52

escofresco · Accepted Answer · 2019-10-19 16:07:14Z

16

As of Python 3, you can explicitly declare variables by type:

x: int = 3

or:

def f(x: int):
    return x

answered Oct 19, 2019 at 16:07

escofresco

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1 Comment

segfault Over a year ago

Will a warning or Exception be raised if I assign a string to it after explicitly declaring as an int?

Ned Batchelder · Accepted Answer · 2010-10-28 10:57:39Z

10

Python has no type declarations. Python 3 introduces something called function annotations, which Guido sometimes refers to as "the thing that isn't type declarations," because the most obvious use of it will be to provide type information as a hint.

As others have mentioned, various IDEs do a better or worse job at auto-completing.

answered Oct 28, 2010 at 10:57

Ned Batchelder

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Comments

mossplix · Accepted Answer · 2010-10-30 19:00:43Z

4

in case you want methods callable on a type ...you can always use dir(var) in python console...

edited Oct 30, 2010 at 19:00

answered Oct 28, 2010 at 12:12

mossplix

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2 Comments

aaronasterling Over a year ago

+1 I think that this is the right answer. Learn the methods available on it the hard way and quit your bellyaching.

GrowingCode247 Over a year ago

@aaronasterling How silly. "Work harder than you have to simply because languages like Python and Javascript make things more difficult than they have to be."

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