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Python is not weakly typed. It is strongly typed in that it forbids operations that are not well-defined. For example, adding a number to a string) rather than

Python is not weakly typed. It is strongly typed in that it forbids operations that are not well-defined. For example, adding a number to a string) rather than silently attempting to make sense of them. I agree wholeheartedly about weakly typed languages, though.

willtim 7y ago
I believe that marketing Python as "strongly typed" has the potential to confuse rather than educate. Python still crashes at runtime with these errors. It has nice error messages, but it still crashes, potentially in production. If you want to create your own "types", you'll have to add your own runtime checks. It's much more sane than JavaScript, but it's not strongly typed like Haskell. Python does not automatically coerce some built-in runtime values, that's it.
- mpcjanssen 7y ago
  You are describing static typing. There is a well defined difference between strongly typed and statically typed.
  - enginaar 7y ago
    Could you elaborate or point to a resource? AFAIK, term "strongly typed" is usually used to refer to that the type cannot change but I'm failing to find a well defined definition or the comparison against statically typed.
    - willtim 7y ago
      The word "type" has a specific meaning in maths/logic, which is not the same as that used by the "dynamic" languages community. Professor Bob Harper of CMU would refer to Python as unityped, i.e. having a single type: https://existentialtype.wordpress.com/2011/03/19/dynamic-languages-are-static-languages/ https://existentialtype.wordpress.com/2011/03/19/dynamic-lan...
    - kbp 7y ago
      Static typing means that types are figured out statically by looking at the source code, and type errors are detected then when it notices a mismatch. Dynamic typing means that types are worked out at runtime by looking at live objects when code operating on them executes. Strong typing means that types cannot be substituted for other types. In C, you can write `int x = "one"` and the char * (address of) "one" is automatically converted to an int, or in Javascript you can write 1 + "2" and a string "1" is automatically created; depending who you're talking to, either or both of these qualify as weak typing. They're both spectrums, and commonly confused with each other.
      - willtim 7y ago
        "Dynamic typing" is really just case analysis at runtime. Every static language is capable of dynamic typing, it's not some feature that statically typed languages lack. A dynamic language is really just a static language with one type.
        kbp 7y ago
        Why aren't statically typed programs really just dynamically typed programs where all the types happen to be statically inferable?
        willtim 7y ago
        Because most statically typed languages allow us to define our own types, add type signatures to constrain etc. Dependently typed languages also allow types to depend on values. Inference is useful, but only one aspect of static typing.
        deleted 7y ago
        [deleted]
      - enginaar 7y ago
        You're explaining static typing vs dynamic typing. I'm still failing to see how different Strong vs Static. If the only difference is "Static" means "types are figured out statically by looking at the source code" do you mean it's possible to change the type unlike strong typing? If not, can we say Static encapsulates Strong?
  - willtim 7y ago
    My point is that your marketing is misleading. Use "strong dynamic types" if you must, but for Python, it would be more accurate to say "strongly tagged".
- kbp 7y ago
  Not automatically coercing values is all that strong typing means. Getting a type error before you run the program is static typing. They're separate axes, and both useful to talk about in a language.
  - willtim 7y ago
    > Not automatically coercing values is all that strong typing means. It's at best a colloquial term and it's misleading to non-technical management.
    - deleted 7y ago
      [deleted]

willtim 7y ago

I believe that marketing Python as "strongly typed" has the potential to confuse rather than educate. Python still crashes at runtime with these errors. It has nice error messages, but it still crashes, potentially in production. If you want to create your own "types", you'll have to add your own runtime checks. It's much more sane than JavaScript, but it's not strongly typed like Haskell. Python does not automatically coerce some built-in runtime values, that's it.

mpcjanssen 7y ago
You are describing static typing. There is a well defined difference between strongly typed and statically typed.
- enginaar 7y ago
  Could you elaborate or point to a resource? AFAIK, term "strongly typed" is usually used to refer to that the type cannot change but I'm failing to find a well defined definition or the comparison against statically typed.
  - willtim 7y ago
    The word "type" has a specific meaning in maths/logic, which is not the same as that used by the "dynamic" languages community. Professor Bob Harper of CMU would refer to Python as unityped, i.e. having a single type: https://existentialtype.wordpress.com/2011/03/19/dynamic-languages-are-static-languages/ https://existentialtype.wordpress.com/2011/03/19/dynamic-lan...
  - kbp 7y ago
    Static typing means that types are figured out statically by looking at the source code, and type errors are detected then when it notices a mismatch. Dynamic typing means that types are worked out at runtime by looking at live objects when code operating on them executes. Strong typing means that types cannot be substituted for other types. In C, you can write `int x = "one"` and the char * (address of) "one" is automatically converted to an int, or in Javascript you can write 1 + "2" and a string "1" is automatically created; depending who you're talking to, either or both of these qualify as weak typing. They're both spectrums, and commonly confused with each other.
    - willtim 7y ago
      "Dynamic typing" is really just case analysis at runtime. Every static language is capable of dynamic typing, it's not some feature that statically typed languages lack. A dynamic language is really just a static language with one type.
      - kbp 7y ago
        Why aren't statically typed programs really just dynamically typed programs where all the types happen to be statically inferable?
        willtim 7y ago
        Because most statically typed languages allow us to define our own types, add type signatures to constrain etc. Dependently typed languages also allow types to depend on values. Inference is useful, but only one aspect of static typing.
        deleted 7y ago
        [deleted]
    - enginaar 7y ago
      You're explaining static typing vs dynamic typing. I'm still failing to see how different Strong vs Static. If the only difference is "Static" means "types are figured out statically by looking at the source code" do you mean it's possible to change the type unlike strong typing? If not, can we say Static encapsulates Strong?
- willtim 7y ago
  My point is that your marketing is misleading. Use "strong dynamic types" if you must, but for Python, it would be more accurate to say "strongly tagged".
kbp 7y ago
Not automatically coercing values is all that strong typing means. Getting a type error before you run the program is static typing. They're separate axes, and both useful to talk about in a language.
- willtim 7y ago
  > Not automatically coercing values is all that strong typing means. It's at best a colloquial term and it's misleading to non-technical management.
  - deleted 7y ago
    [deleted]