next »

[isthisthingon]

While reading about Python I ran across something that made me stop and think.  Python is considered to be a “strongly typed” language.  Well perhaps I’m alone in missing this subtle yet critical distinction.  However, once I realized that Python is strongly typed as well as dynamically typed, I wanted to share what I read.

The four categories of language typing are:  static/dynamic and strong/weak.  Although I can't recall a language that is both statically typed and weakly typed, it is possible given the definitions.  So here's a breakdown and clarification of each category (From “Dive Into Python"):

• Statically typed language: A language in which types are fixed at compile time. Most statically typed languages enforce this by requiring you to declare all variables with their datatypes before using them. Java and C are statically typed languages.
• Dynamically typed language: A language in which types are discovered at execution time; the opposite of statically typed. VBScript and Python are dynamically typed, because they figure out what type a variable is when you first assign it a value.
• Strongly typed language: A language in which types are always enforced. Java and Python are strongly typed. If you have an integer, you can't treat it like a string without explicitly converting it.
• Weakly typed language: A language in which types may be ignored; the opposite of strongly typed. VBScript is weakly typed. In VBScript, you can concatenate the string '12' and the integer 3 to get the string '123', then treat that as the integer 123, all without any explicit conversion.

So Python is both dynamically typed (because it doesn't use explicit datatype declarations) and strongly typed (because once a variable has a datatype, it actually matters).

[nop_90]

It is a "strongly dynamically typed" language
If you look how u make "C" extensions in python then this all makes sense.

Nutshell view (not accurate just for illustration).
Every data type in python inherites from a "C" structure.
which is like this
struct pythonObject :
    type -> type of the object
    data -> what object contains.

you then can make ur own data types, add functions etc.
So python has a string type that inherits off pythonObject.

when u do operations if datatypes do not match or can not be converted an exception occurs.
(little more complex then that but u get the idea )
   

In contrast TCL is a weakly typed language. All data types are a string which are converted to the appropriate type depending on the operation. There is advantages to this when passing data back and forth from C, it is just a string.

[isthisthingon]

Thanks nop!