Usage of pypy compiler

Question

Is there a difference in python programming while using just python and while using pypy compiler? I wanted to try using pypy so that my program execution time becomes faster. Does all the syntax that work in python works in pypy too? If there is no difference, can you tell me how can i install pypy on debian lunux and some usage examples on pypy? Google does not contain much info on pypy other than its description.

Answer 1

From the pypy features page:

PyPy 1.9 implements Python 2.7.2 and runs on Intel x86 (IA-32) and x86_64 platforms, with ARM and PPC being underway. It supports all of the core language, passing the Python test suite.

This means that pretty much any code that you've written in Python 2.7 will work. The only exceptions worth mentioning are some python extensions written in C, such as numpy.

Installation should be fairly easy, you can download a linux binary from here. Then simply extract the interpreter. From this point, you can run your python programs similar to how you would run them with the normal python interpreter.

At the command line, instead of:

python my_program.py

Use:

path/to/where/you/installed/pypy my_program.py

For examples of how/why you might want to use pypy, check out this video from PyCon 2012.

Answer 2

pypy is a compliant alternative implementation of the python language. This means that there are few (intentional) differences. One of the few differences is pypy does not use reference counting. This means, for instance, you have to manually close your files, they will not be automatically closed when your file variable goes out of scope as in CPython.