By: Python Documentation Team Viewed: 153406 times Printer Friendly Format
When a module is imported for the first time (or when the source is more recent than the current compiled file) a .pyc file containing the compiled code should be created in the same directory as the .py file.
One reason that a .pyc file may not be created is permissions problems with the directory. This can happen, for example, if you develop as one user but run as another, such as if you are testing with a web server. Creation of a .pyc file is automatic if you’re importing a module and Python has the ability (permissions, free space, etc...) to write the compiled module back to the directory.
Running Python on a top level script is not considered an import and no .pyc will be created. For example, if you have a top-level module abc.py that imports another module xyz.py, when you run abc, xyz.pyc will be created since xyz is imported, but no abc.pyc file will be created since abc.py isn’t being imported.
If you need to create abc.pyc – that is, to create a .pyc file for a module that is not imported – you can, using the py_compile and compileall modules.
The py_compile module can manually compile any module. One way is to use the compile() function in that module interactively:
>>> import py_compile
This will write the .pyc to the same location as abc.py (or you can override that with the optional parameter cfile).
You can also automatically compile all files in a directory or directories using the compileall module. You can do it from the shell prompt by running compileall.py and providing the path of a directory containing Python files to compile:
python -m compileall .
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