5 ms·

> I regularly wish python required some sort type indication for function parameters You can use type annotations, either via the builtin lib or 3rd party libs

by closed 8y ago

> I regularly wish python required some sort type indication for function parameters You can use type annotations, either via the builtin lib or 3rd party libs! https://docs.python.org/3/library/typing.html https://docs.python.org/3/library/typing.html > do_x() if a.y() I feel this. You can use `a.y() and do_x()`, but I'm not sure how people would react :o

fhood 8y ago
> You can use type annotations, either via the builtin lib or 3rd party libs! > https://docs.python.org/3/library/typing.html https://docs.python.org/3/library/typing.html I know, but tragically, because I am not forced to, I never do. I do appreciate that feature though. Maybe this will be the impetus I need to start taking advantage of it.
- computerfriend 8y ago
  I started doing this about a year ago and it has made me a better Python developer. Getting into the habit of always writing a type annotation was hard at first, but you quickly get used to it. It helps if you configure mypy to complain at you if the annotations are missing.
- dharmab 8y ago
  If you're starting a new project you can force yourself by running mypy's strict mode in CI.
- lmm 8y ago
  You'll have a much better experience in an ecosystem where typing is the widespread expectation, IME. Try an ML-family language if you haven't already - I find they combine the best parts of something like Python and something like Java. There was a post pushing F# earlier today.
bakery2k 8y ago
> `a.y() and do_x()` If you're happy to write it that way round, why not just use `if a.y(): do_x()`?
- fhood 8y ago
  Against pep-8 standards. I do end up using that sytax quite a bit anyway though.
  - viraptor 8y ago
    > PEP8: This document gives coding conventions for the Python code comprising the standard library in the main Python distribution. It's fine not to follow PEP8 for your own software. It's a useful guide, not a law.
- closed 8y ago
  It's worth noting the second can't be used inline. I don't know the history, but it seems like that might be one of the reasons `x() if y()` isn't allowed in python. [x() if y()] if it existed, might carry an explicit else None. On the other hand [x() and y()] does something different when y() is falsey.
  - vram22 8y ago
    >I don't know the history, but it seems like that might be one of the reasons `x() if y()` isn't allowed in python. Maybe I misunderstood your context, but if not, conditional expressions do exist in Python: $ python Python 2.7.12 |Anaconda 4.2.0 (32-bit)| (default, Jun 29 2016, 11:42:13) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. Anaconda is brought to you by Continuum Analytics. Please check out: http://continuum.io/thanks and https://anaconda.org >>> 1 if 1 == 1 else 2 1 >>> 2 if 1 == 1 else 2 2 >>> ^Z $ py -3 Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> 1 if 1 == 1 else 2 1 >>> 2 if 1 == 1 else 2 2 >>> Using nested conditional expressions to classify characters: https://jugad2.blogspot.com/2017/04/using-nested-conditional-expressions-to.html https://jugad2.blogspot.com/2017/04/using-nested-conditional...
    - vram22 8y ago
earenndil 8y ago
Type annotations don't seem to actually have any effect, though? Consider: >>> def add(a: int, b: int): ... return a+b ... >>> add("a", "b") 'ab' This should be an error, even if it's a runtime error.
- camel_Snake 8y ago
  it's optional typing. Running it through mypy will result in an error. If you are using type annotations I don't see why you wouldn't also be using a proper IDE or testing your code.
- bakery2k 8y ago
  There doesn't seem to be any interest in checking type annotations at run-time. Unfortunately, without doing so, type annotations look authoritative but are essentially just comments. I believe Julia is an example of a dynamically-typed language which does perform such checks at run-time - including as part of its support for multiple dispatch.
  - nitely 8y ago
    Make mypy type checking part of the CI pipeline. Done.
  - qquark 8y ago
    I've been using enforce for this purpose (https://github.com/RussBaz/enforce https://github.com/RussBaz/enforce). It provides decorators that enable type checking where wanted. This gives the advantage of migrating existing code to type checking at your own pace at least. On a general note I've come across a few cases, when pushing python's type annotations to their limits, that force you to put the type names in string quotes, and that makes the whole thing feel like a hack. It's better than nothing for my use cases, but if I remember correctly both mypy and enforce have problems in common that are probably coming from the way python itself is built, such as self reference in a class definition.
    - quodlibetor 8y ago

by closed 8y ago

fhood 8y ago

> You can use type annotations, either via the builtin lib or 3rd party libs! > https://docs.python.org/3/library/typing.html https://docs.python.org/3/library/typing.html I know, but tragically, because I am not forced to, I never do. I do appreciate that feature though. Maybe this will be the impetus I need to start taking advantage of it.

computerfriend 8y ago
I started doing this about a year ago and it has made me a better Python developer. Getting into the habit of always writing a type annotation was hard at first, but you quickly get used to it. It helps if you configure mypy to complain at you if the annotations are missing.
dharmab 8y ago
If you're starting a new project you can force yourself by running mypy's strict mode in CI.
lmm 8y ago
You'll have a much better experience in an ecosystem where typing is the widespread expectation, IME. Try an ML-family language if you haven't already - I find they combine the best parts of something like Python and something like Java. There was a post pushing F# earlier today.

bakery2k 8y ago

> `a.y() and do_x()` If you're happy to write it that way round, why not just use `if a.y(): do_x()`?

fhood 8y ago
Against pep-8 standards. I do end up using that sytax quite a bit anyway though.
- viraptor 8y ago
  > PEP8: This document gives coding conventions for the Python code comprising the standard library in the main Python distribution. It's fine not to follow PEP8 for your own software. It's a useful guide, not a law.
closed 8y ago
It's worth noting the second can't be used inline. I don't know the history, but it seems like that might be one of the reasons `x() if y()` isn't allowed in python. [x() if y()] if it existed, might carry an explicit else None. On the other hand [x() and y()] does something different when y() is falsey.
- vram22 8y ago
  >I don't know the history, but it seems like that might be one of the reasons `x() if y()` isn't allowed in python. Maybe I misunderstood your context, but if not, conditional expressions do exist in Python: $ python Python 2.7.12 |Anaconda 4.2.0 (32-bit)| (default, Jun 29 2016, 11:42:13) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. Anaconda is brought to you by Continuum Analytics. Please check out: http://continuum.io/thanks and https://anaconda.org >>> 1 if 1 == 1 else 2 1 >>> 2 if 1 == 1 else 2 2 >>> ^Z $ py -3 Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> 1 if 1 == 1 else 2 1 >>> 2 if 1 == 1 else 2 2 >>> Using nested conditional expressions to classify characters: https://jugad2.blogspot.com/2017/04/using-nested-conditional-expressions-to.html https://jugad2.blogspot.com/2017/04/using-nested-conditional...
  - vram22 8y ago

earenndil 8y ago

Type annotations don't seem to actually have any effect, though? Consider: >>> def add(a: int, b: int): ... return a+b ... >>> add("a", "b") 'ab' This should be an error, even if it's a runtime error.

camel_Snake 8y ago
it's optional typing. Running it through mypy will result in an error. If you are using type annotations I don't see why you wouldn't also be using a proper IDE or testing your code.
bakery2k 8y ago
There doesn't seem to be any interest in checking type annotations at run-time. Unfortunately, without doing so, type annotations look authoritative but are essentially just comments. I believe Julia is an example of a dynamically-typed language which does perform such checks at run-time - including as part of its support for multiple dispatch.
- nitely 8y ago
  Make mypy type checking part of the CI pipeline. Done.
- qquark 8y ago
  I've been using enforce for this purpose (https://github.com/RussBaz/enforce https://github.com/RussBaz/enforce). It provides decorators that enable type checking where wanted. This gives the advantage of migrating existing code to type checking at your own pace at least. On a general note I've come across a few cases, when pushing python's type annotations to their limits, that force you to put the type names in string quotes, and that makes the whole thing feel like a hack. It's better than nothing for my use cases, but if I remember correctly both mypy and enforce have problems in common that are probably coming from the way python itself is built, such as self reference in a class definition.
  - quodlibetor 8y ago