[Python] What is the difference between PyPy and Python? are there lot of differences?

One of the main difference is that pypy supports only R-Python, which stands
for 'Restricted Python".

It is a subset of C-python language.

See here for more info:
http://codespeak.net/pypy/dist/pypy/doc/coding-guide.html#rpython-definition-not

Cheers

This is wrong. The PyPy *interpreter* is written in RPython. At the
application level, PyPy supports the full syntax and semantics of
Python (with a few minor differences of the same sort that you find in
Jython or IronPython).

I stand corrected. Thanks Ian

Cheers

PyPy (2.7) and Jython (2.5) are pretty close to each other, though PyPy is
quite a bit faster than Jython or CPython. Both PyPy and Jython are good
implementations of the Python language, at least if you don't need a lot of
C extension modules.

IronPython doesn't appear to have a standard library. :( Or rather, it can
use a CPython install's standard library, but a significant fraction of it
doesn't work on IronPython - it doesn't appear to have been tested or
adapted. There's something called FePy that includes IronPython and a
better standard library, but AFAIK, it only works on windows.

Not true. PyPy is *written* in rpython. It runs standard Python.

Python is a language; PyPy is one implementation of that language. The
"classic" implementation of Python is CPython, not to be confused with
Cython; there are a few others as well. If you talk of "installing
Python", it probably means CPython.
Sloppy but brief explanation: Python's variables are typeless; its
objects are strongly typed.

Longer explanation: Every piece of data in Python is an object.
Objects can be referenced by names; one object can have more than one
name pointing to it. Any name can point to any value, which is
somewhat the opposite of "strongly-typed variables" in other
languages. For instance:

a = "Hello" # a points to or "holds" a string
a = 234 # a now points to an integer
a = 1.0 # a now points to a float
a = [1,2,3] # a now has a list (array)

In debugging, all you generally care about is "what does this object
point to". I guess whether or not this makes things easier or harder
depends a lot on what sort of bugs you're tracking down.

Hope that helps!

Chris Angelico

Thanks Chris,
That was a nice brief explanation,but i got the point.

Python is strongly typed. There are no static type checks in Python.
Type checks are done at runtime. Dynamic typing does not mean that
Python is a weakly typed language.

The question of debugging is often raised, particularly by Java heads:

In Python, the "doctest" and "unittest" modules can be used to verify
that code works according to specification (e.g. trap type errors),
and are common alternatives to static type checks.

http://docs.python.org/release/3.2/library/doctest.html
http://docs.python.org/release/3.2/library/unittest.html

It is a good practice to always write tests for your code.

Python 3.x also has function argument and return value type
annotations, which is a further guard against type errors:

http://www.python.org/dev/peps/pep-3107/


Sturla