Python VS Cpython

Python vs Cpython

So what is CPython?

CPython is the original Python implementation. It is the implementation you download from Python.org. People call it CPython to distinguish it from other, later, Python implementations, and to distinguish the implementation of the language engine from the Python programming language itself.

The latter part is where your confusion comes from; you need to keep Python-the-language separate from whatever runs the Python code.

CPython happens to be implemented in C. That is just an implementation detail, really. CPython compiles your Python code into bytecode (transparently) and interprets that bytecode in a evaluation loop.

CPython is also the first to implement new features; Python-the-language development uses CPython as the base; other implementations follow.

What about Jython, etc.?

Jython, IronPython and PyPy are the current "other" implementations of the Python programming language; these are implemented in Java, C# and RPython (a subset of Python), respectively. Jython compiles your Python code to Java bytecode, so your Python code can run on the JVM. IronPython lets you run Python on the Microsoft CLR. And PyPy, being implemented in (a subset of) Python, lets you run Python code faster than CPython, which rightly should blow your mind. :-)

Actually compiling to C

So CPython does not translate your Python code to C by itself. Instead, it runs an interpreter loop. There is a project that does translate Python-ish code to C, and that is called Cython. Cython adds a few extensions to the Python language, and lets you compile your code to C extensions, code that plugs into the CPython interpreter.

Is there any difference between cpython and python

Python is a language.

CPython is the default byte-code interpreter of Python, which is written in C.

There is also other implementation of Python such as IronPython (for .NET), Jython (for Java), etc.

What is the use of Cpython , IronPython , Jython ? Is it used in the process of code conversion from Python to Machine code?

Python is a language. CPython, IronPython, Jython are different implementations of this langauge. They also all happen to be implemented in different languages themselves: CPython is written in C, IronPython in .NET, and Jython in Java. Thus, it is very easy to integrate IronPython into a .NET program, and it is really easy to embed Jython into a Java program. But for the most part, when people execute Python, they are running their Python code through CPython (even if they don't know that's what it's officially called). It is the original Python implementation, it is the fastest of them, as well as being the implementation that defines what Python is. Unless you want to use Python within .NET or Java frameworks, you might never encounter the other two.

what's the differences python3 and pypy3

Kindly check this, when we speak of Python programming language we often mean not just the language but also the implementation. Python is a specification for a language that can be implemented in many different ways.

The default implementation of the Python programming language is Cpython(assuming python3 you mean Cpython). As the name suggests Cpython is written in C language. Cpython compiles the python source code into intermediate bytecode, which is executed by the Cpython virtual machine.

Jython is an implementation of the Python programming language that can run on the Java platform. Jython programs use Java classes instead of Python modules. Jython compiles into Java byte code, which can then be run by Java virtual machine.

PyPy
If you want your code to run faster, you should probably just use PyPy. — Guido van Rossum (creator of Python)
Python is a dynamic programming language. Python is said to be slow as the default CPython implementation compiles the python source code in bytecode which is slow as compared to machine code(native code). Here PyPy comes in.

PyPy is an implementation of the Python programming language written in Python. The Interpreter is written in RPython (a subset of Python).
PyPy uses Just In Time (JIT) compilation. In simple terms, JIT uses compilation methods to make the interpreter system more efficient and fast. So basically JIT makes it possible to compile the source code into native machine code which makes it very fast.
PyPy also comes with default support for stackless mode, providing micro-threads for massive concurrency. It is said to be approximately 7.5 times faster than Cpython.

Hope this will help you.

What does Default Implementation of Python means in CPython?

There's one group of developers which work on the Python language. The "Python language" could just be an abstract specification of how the language is supposed to behave, with no actual runnable project. But that's not what those Python developers do; they produce the "Python language" both in the abstract as a series of suggestions and documentation, but they also implement that in the CPython language. CPython is an implementation of the Python language, written in C. "The Python language" in the abstract (specifications, documentation) and in its actual implementation in the form of CPython go hand in hand.

There are other groups of developers implementing alternative versions of the Python language; they behave the same (for the most part) in that they can execute Python code conforming to the abstract language definition, but the Python implementation is not the aforementioned CPython, but something else.

PyPy vs. CPython 3.8 - Difference in number of iterations with the same code?

I've stepped through your code in two concurrent debugging sessions, one for each interpreter. The sets in self.mask do not look the same between the two interpreters - they contain the same values, but in a different order. Even on the second recursion of solve (when self.iterations becomes 2), the flow of execution diverges because of this difference. I don't know if that's the exact cause of the discrepancy you're seeing, but I'm guessing it has to do with sets having guaranteed insertion order in one implementation, and not in another.

Why shouldn't I use PyPy over CPython if PyPy is 6.3 times faster?

NOTE: PyPy is more mature and better supported now than it was in 2013, when this question was asked. Avoid drawing conclusions from out-of-date information.

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1. PyPy, as others have been quick to mention, has tenuous support for C extensions. It has support, but typically at slower-than-Python speeds and it's iffy at best. Hence a lot of modules simply require CPython. PyPy doesn't support numpy. Some extensions are still not supported (Pandas, SciPy, etc.), take a look at the list of supported packages before making the change. Note that many packages marked unsupported on the list are now supported.
2. Python 3 support is experimental at the moment. has just reached stable! As of 20th June 2014, PyPy3 2.3.1 - Fulcrum is out!
3. PyPy sometimes isn't actually faster for "scripts", which a lot of people use Python for. These are the short-running programs that do something simple and small. Because PyPy is a JIT compiler its main advantages come from long run times and simple types (such as numbers). PyPy's pre-JIT speeds can be bad compared to CPython.
4. Inertia. Moving to PyPy often requires retooling, which for some people and organizations is simply too much work.

Those are the main reasons that affect me, I'd say.

Global Interpreter lock: Jython vs CPython

Yes, Jython uses Java-Threads (even if you're using the threading modul of Python) and so it has no GIL. But this isn't the answer (otherwise it has to be 42, because the question is unclear :^) ).
The better Question is, what criteria you have and if CPython or Jython would be better.

If you want real multithreadding, it's your thing.
If you want to use Java and Python, use it.
If you want fast execution times .... then are other languages maybe better (you can try to messure the time in a thread task in Python and the same code in Jython, but I guess even with GIL CPython would be faster).

Greets,
Zonk

what is Cpython is this single module or complete Python

CPython is the “official,” or reference implementation of Python. If you are installing python from python.org you are running Cpython implementation. You can confirm this via platform module.

>>> import platform
>>> platform.python_implementation()
'Cpython'

CPython contains complete implementation of the language(Including standard library/compiler/Byte Code Interpreter etc). If you want to understand how the source code is laid out you can refer Your Guide to the CPython Source Code.

Additional reference:
Python vs Cpython

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