What is pycache

Question

From what I understand  a cache is an encrypted file of similar files   What do we do with the   pycache   folder  Is it what we give to people instead of our source code  Is it just my input data  This folder keeps getting created  what it is for

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Python Version 2 x will have  pyc when interpreter compiles the code   Python Version 3 x will have   pycache   when interpreter compiles the code   alok alok    ls module py  module pyc    pycache    test py alok alok

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When you import a module   import file name   Python stores the compiled bytecode in   pycache   directory so that future imports can use it directly  rather than having to parse and compile the source again   It does not do that for merely running a script  only when a file is imported     Previous versions used to store the cached bytecode as  pyc files that littered up the same directory as the  py files  but starting in Python 3 they were moved to a subdirectory to make things tidier    PYTHONDONTWRITEBYTECODE  ---  If this is set to a non-empty string  Python won   t try to write  pyc files on the import of source modules  This is equivalent to specifying the -B option

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Updated answer from 3 7  docs      To speed up loading modules  Python caches the compiled version of   each module in the   pycache   directory under the name   module version pyc  where the version encodes the format of the   compiled file  it generally contains the Python version number  For   example  in CPython release 3 3 the compiled version of spam py would   be cached as   pycache   spam cpython-33 pyc  This naming convention   allows compiled modules from different releases and different versions   of Python to coexist    Source  https   docs python org 3 tutorial modules html compiled-python-files  That is  this directory is generated by Python and exists to make your programs run faster  It shouldn t be committed to source control  and should coexist in peace with your local source code       pycache   is a directory that contains bytecode cache files that are automatically generated by python  namely compiled python  or  pyc  files  You might be wondering why Python  an  interpreted  language  has any compiled files at all  This SO question addresses that  and it s definitely worth reading this answer    The python docs go into more depth about exactly how it works and why it exists    It was added in python 3 2 because the existing system of maintaining  pyc files in the same directory caused various problems  such as when a program was run with Python interpreters of different versions  For the full feature spec  see PEP 3174

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A   pycache   folder is created when you use the line   import file name   or try to get information from another file you have created  This makes it a little faster when running your program the second time to open the other file

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In 3 2 and later  Python saves  pyc compiled byte code files in a sub-directory named   pycache   located in the directory where your source files reside with filenames that identify the Python version that created them  e g  script cpython-33 pyc

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pycache   is a folder containing Python 3 bytecode compiled and ready to be executed  I don t recommend routinely deleting these files or suppressing creation during development as it may hurt performance  Just have a recursive command ready  see below  to clean up when needed as bytecode can become stale in edge cases  see comments   Python programmers usually ignore bytecode  Indeed   pycache   and   pyc are common lines to see in  gitignore files  Bytecode is not meant for distribution and can be disassembled using dis module   If you are using OS X you can easily hide all of these folders in your project by running following command from the root folder of your project  find   -name    pycache    -exec chflags hidden        Replace   pycache   with   pyc for Python 2  This sets a flag on all those directories   pyc files  telling  Finder Textmate 2 to exclude them from listings  Importantly the bytecode is there  it s just hidden  Rerun the command if you create new modules and wish to hide new bytecode or if you delete the hidden bytecode files   On Windows the equivalent command might be  not tested  batch script welcome   dir    s b   findstr   pycache     attrib  h  s  r  Which is same as going through the project hiding folders using right-click  gt  hide     Running unit tests is one scenario  more in comments  where deleting the   pyc files and   pycache   folders is indeed useful  I use the following lines in my    bash profile and just run cl to clean up when needed  alias cpy  find   -name  quot   pycache   quot  -delete  alias cpc  find   -name  quot   pyc quot        -delete      alias cl  cpy  amp  amp  cpc  amp  amp        and more lately   pip install pyclean pyclean

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When you run a program in python  the interpreter compiles it to bytecode first  this is an oversimplification  and stores it in the   pycache   folder  If you look in there you will find a bunch of files sharing the names of the  py files in your project s folder  only their extensions will be either  pyc or  pyo  These are bytecode-compiled and optimized bytecode-compiled versions of your program s files  respectively  As a programmer  you can largely just ignore it    All it does is make your program start a little faster  When your scripts change  they will be recompiled  and if you delete the files or the whole folder and run your program again  they will reappear  unless you specifically suppress that behavior   When you re sending your code to other people  the common practice is to delete that folder  but it doesn t really matter whether you do or don t  When you re using version control  git   this folder is typically listed in the ignore file   gitignore  and thus not included  If you are using cpython  which is the most common  as it s the reference implementation  and you don t want that folder  then you can suppress it by starting the interpreter with the -B flag  for example python -B foo py  Another option  as noted by tcaswell  is to set the environment variable PYTHONDONTWRITEBYTECODE to any value  according to python s man page  any  quot non-empty string quot

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from the official python tutorial Modules     To speed up loading modules  Python caches the compiled version of each module in the   pycache   directory under the name module version pyc  where the version encodes the format of the compiled file  it generally contains the Python version number  For example  in CPython release 3 6 the compiled version of spam py would be cached as   pycache   spam cpython-36 pyc    from Python doc Programming FAQs     When a module is imported for the first time  or when the source file has changed since the current compiled file was created  a  pyc file containing the compiled code should be created in a   pycache   subdirectory of the directory containing the  py file  The  pyc file will have a filename that starts with the same name as the  py file  and ends with  pyc  with a middle component that depends on the particular python binary that created it

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Execution of a python script would cause the byte code to be generated in memory and kept until the program is shutdown  In case a module is imported  for faster reusability  Python would create a cache  pyc  PYC is  Python   Compiled   file where the byte code of the module being imported is cached  Idea is to speed up loading of python modules by avoiding re-compilation   compile once  run multiple times policy   when they are re-imported   The name of the file is the same as the module name  The part after the initial dot indicates Python implementation that created the cache  could be CPython  followed by its version number

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The python interpreter compiles the   py script file and saves the results of the compilation to the   pycache   directory   When the project is executed again  if the interpreter identifies that the   py script has not been modified  it skips the compile step and runs the previously generated   pyc file stored in the   pycache   folder   When the project is complex  you can make the preparation time before the project is run shorter  If the program is too small  you can ignore that by using python -B abc py with the B option

[python] What is pycache?

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[python] What is pycache?