How to avoid pyc files

Question

Can I run the python interpreter without generating the compiled  pyc files

User · Answer

There actually IS a way to do it in Python 2.3+, but it's a bit esoteric. I don't know if you realize this, but you can do the following:

$ unzip -l /tmp/example.zip
 Archive:  /tmp/example.zip
   Length     Date   Time    Name
 --------    ----   ----    ----
     8467  11-26-02 22:30   jwzthreading.py
 --------                   -------
     8467                   1 file
$ ./python
Python 2.3 (#1, Aug 1 2003, 19:54:32) 
>>> import sys
>>> sys.path.insert(0, '/tmp/example.zip')  # Add .zip file to front of path
>>> import jwzthreading
>>> jwzthreading.__file__
'/tmp/example.zip/jwzthreading.py'

According to the zipimport library:

Any files may be present in the ZIP archive, but only files .py and .py[co] are available for import. ZIP import of dynamic modules (.pyd, .so) is disallowed. Note that if an archive only contains .py files, Python will not attempt to modify the archive by adding the corresponding .pyc or .pyo file, meaning that if a ZIP archive doesn't contain .pyc files, importing may be rather slow.

Thus, all you have to do is zip the files up, add the zipfile to your sys.path and then import them.

If you're building this for UNIX, you might also consider packaging your script using this recipe: unix zip executable, but note that you might have to tweak this if you plan on using stdin or reading anything from sys.args (it CAN be done without too much trouble).

In my experience performance doesn't suffer too much because of this, but you should think twice before importing any very large modules this way.

User · Answer

import sys  sys dont write bytecode   True

User · Answer

From  What   s New in Python 2 6 - Interpreter Changes       Python can now be prevented from   writing  pyc or  pyo files by   supplying the -B switch to the Python   interpreter  or by setting the   PYTHONDONTWRITEBYTECODE environment   variable before running the   interpreter  This setting is available   to Python programs as the   sys dont write bytecode variable  and   Python code can change the value to   modify the interpreter   s behaviour    Update 2010-11-27  Python 3 2 addresses the issue of cluttering source folders with  pyc files by introducing a special   pycache   subfolder  see What s New in Python 3 2 - PYC Repository Directories

User · Answer

I have several test cases in a test suite and before I was running the test suite in the Mac Terminal like this    python LoginSuite py   Running the command this way my directory was being populated with  pyc files  I tried the below stated method and it solved the issue   python -B LoginSuite py   This method works if you are importing test cases into the test suite and running the suite on the command line

User · Answer

In 2 5  theres no way to suppress it  other than measures like not giving users write access to the directory   In python 2 6 and 3 0 however  there may be a setting in the sys module called  dont write bytecode  that can be set to suppress this   This can also be set by passing the  -B  option  or setting the environment variable  PYTHONDONTWRITEBYTECODE

User · Answer

You could make the directories that your modules exist in read-only for the user that the Python interpreter is running as   I don t think there s a more elegant option  PEP 304 appears to have been an attempt to introduce a simple option for this  but it appears to have been abandoned   I imagine there s probably some other problem you re trying to solve  for which disabling  py co  would appear to be a workaround  but it ll probably be better to attack whatever this original problem is instead

User · Answer

You can set sys dont write bytecode   True in your source  but that would have to be in the first python file loaded  If you execute python somefile py then you will not get somefile pyc   When you install a utility using setup py and entry points  you will have set sys dont write bytecode in the startup script  So you cannot rely on the  default  startup script generated by setuptools   If you start Python with python file as argument yourself you can specify -B   python -B somefile py   somefile pyc would not be generated anyway  but no  pyc files for other files imported too   If you have some utility myutil and you cannot change that  it will not pass -B to the python interpreter  Just start it by setting the environment variable PYTHONDONTWRITEBYTECODE   PYTHONDONTWRITEBYTECODE x myutil

User · Answer

Solution for ipython 6 2 1 using python 3 5 2  Tested on Ubuntu 16 04 and Windows 10    Ipython doesn   t respect  env PYTHONDONTWRITEBYTECODE  1 if set in the ipython interpretor or during startup in    ipython profile-default startup 00-startup ipy  Instead using the following in your   ipython profile-default startup 00-startup py    import sys sys dont write bytecode True

User · Answer

Starting with Python 3 8 you can use the environment variable PYTHONPYCACHEPREFIX to define a cache directory for Python   From the Python docs      If this is set  Python will write  pyc files in a mirror directory tree at this path  instead of in pycache directories within the source tree  This is equivalent to specifying the -X pycache prefix PATH option    Example  If you add the following line to your   profile in Linux   export PYTHONPYCACHEPREFIX   HOME  cache cpython     Python won t create the annoying   pycache   directories in your project directory  instead it will put all of them under    cache cpython

User · Answer

As far as I know python will compile all modules you  import   However python will NOT compile a python script run using   python script py   it will however compile any modules that the script imports    The real questions is why you don t want python to compile the modules  You could probably automate a way of cleaning these up if they are getting in the way

[python] How to avoid .pyc files?

Examples related to python