Re: questions from a lost sheep

[johannes raggam]

On Thu, 2008-10-02 at 15:18 -0500, sk**@pobox.com wrote:

JoeI've started to think fondly of the rock-solid stability of Python,
Joeand have been wondering if perhaps aggressive unit testing could
Joemitigate most of the problems of weak typing.

Note: Python is not weakly typed. It is dynamically typed. But, yes,
there is no substitute for unit tests in a language like Python.

just to make it maybe clearer - here an excerpt from the excellent book
dive into python, which is also free available:

"""
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).
"""
http://diveintopython.org/getting_to...s.html#d0e4188
cheers, hannes

[Larry Bates]

johannes raggam wrote:

On Thu, 2008-10-02 at 15:18 -0500, sk**@pobox.com wrote:

>JoeI've started to think fondly of the rock-solid stability of Python,
Joeand have been wondering if perhaps aggressive unit testing could
Joemitigate most of the problems of weak typing.

Note: Python is not weakly typed. It is dynamically typed. But, yes,
there is no substitute for unit tests in a language like Python.

just to make it maybe clearer - here an excerpt from the excellent book
dive into python, which is also free available:

"""
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).
"""
http://diveintopython.org/getting_to...s.html#d0e4188
cheers, hannes

That is a GREAT explanation of statically, dynamically, strongly and weakly
typed languages. So many programmers are confused about these differences. Many
believe that statically typed is the only way to have strongly typed and they
are incorrect. Thanks for this.

-Larry

[Michele Simionato]

On Oct 2, 11:08*pm, johannes raggam <[e-mail]:

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.

I have always considered this argument rather weak.
It is true, we Pythonista we are in a better position
that Perl and VBScript users, but still how strong is
"strong" typing really? When I can never know the types
accepted by a function at compile time?
When I can change the class of
an object at runtime?
Dynamic typing has its advantages, but calling it "strong" is
ridicolous for people coming from a background in ML or Haskell. The
definitions change
according to the circles you frequent, so there will be always
confusions on the terminology, unfortunately.