compileall — Byte-compile Python libraries

Source code: Lib/compileall.py

This module provides some utility functions to support installing Python libraries. These functions compile Python source files in a directory tree. This module can be used to create the cached byte-code files at library installation time, which makes them available for use even by users who don’t have write permission to the library directories.

Availability: not WASI.

This module does not work or is not available on WebAssembly. See WebAssembly platforms for more information.

Command-line use

This module can work as a script (using python -m compileall) to compile Python sources.

directory ...
file ...

Positional arguments are files to compile or directories that contain source files, traversed recursively. If no argument is given, behave as if the command line was -l <directories from sys.path>.

-l

Do not recurse into subdirectories, only compile source code files directly contained in the named or implied directories.

-f

Force rebuild even if timestamps are up-to-date.

-q

Do not print the list of files compiled. If passed once, error messages will still be printed. If passed twice (-qq), all output is suppressed.

-d destdir

Directory prepended to the path to each file being compiled. This will appear in compilation time tracebacks, and is also compiled in to the byte-code file, where it will be used in tracebacks and other messages in cases where the source file does not exist at the time the byte-code file is executed.

-s strip_prefix
-p prepend_prefix

Remove (-s) or append (-p) the given prefix of paths recorded in the .pyc files. Cannot be combined with -d.

-x regex

regex is used to search the full path to each file considered for compilation, and if the regex produces a match, the file is skipped.

-i list

Read the file list and add each line that it contains to the list of files and directories to compile. If list is -, read lines from stdin.

-b

Write the byte-code files to their legacy locations and names, which may overwrite byte-code files created by another version of Python. The default is to write files to their PEP 3147 locations and names, which allows byte-code files from multiple versions of Python to coexist.

-r

Control the maximum recursion level for subdirectories. If this is given, then -l option will not be taken into account. python -m compileall <directory> -r 0 is equivalent to python -m compileall <directory> -l.

-j N

Use N workers to compile the files within the given directory. If 0 is used, then the result of os.process_cpu_count() will be used.

--invalidation-mode [timestamp|checked-hash|unchecked-hash]

Control how the generated byte-code files are invalidated at runtime. The timestamp value, means that .pyc files with the source timestamp and size embedded will be generated. The checked-hash and unchecked-hash values cause hash-based pycs to be generated. Hash-based pycs embed a hash of the source file contents rather than a timestamp. See Cached bytecode invalidation for more information on how Python validates bytecode cache files at runtime. The default is timestamp if the SOURCE_DATE_EPOCH environment variable is not set, and checked-hash if the SOURCE_DATE_EPOCH environment variable is set.

-o level

Compile with the given optimization level. May be used multiple times to compile for multiple levels at a time (for example, compileall -o 1 -o 2).

-e dir

Ignore symlinks pointing outside the given directory.

If two .pyc files with different optimization level have the same content, use hard links to consolidate duplicate files.

Changed in version 3.2: Added the -i, -b and -h options.

Changed in version 3.5: Added the -j, -r, and -qq options. -q option was changed to a multilevel value. -b will always produce a byte-code file ending in .pyc, never .pyo.

Changed in version 3.7: Added the --invalidation-mode option.

Changed in version 3.9: Added the -s, -p, -e and --hardlink-dupes options. Raised the default recursion limit from 10 to sys.getrecursionlimit(). Added the possibility to specify the -o option multiple times.

There is no command-line option to control the optimization level used by the compile() function, because the Python interpreter itself already provides the option: python -O -m compileall.

Similarly, the compile() function respects the sys.pycache_prefix setting. The generated bytecode cache will only be useful if compile() is run with the same sys.pycache_prefix (if any) that will be used at runtime.

Public functions

compileall.compile_dir(dir, maxlevels=sys.getrecursionlimit(), ddir=None, force=False, rx=None, quiet=0, legacy=False, optimize=-1, workers=1, invalidation_mode=None, *, stripdir=None, prependdir=None, limit_sl_dest=None, hardlink_dupes=False)

Recursively descend the directory tree named by dir, compiling all .py files along the way. Return a true value if all the files compiled successfully, and a false value otherwise.

The maxlevels parameter is used to limit the depth of the recursion; it defaults to sys.getrecursionlimit().

If ddir is given, it is prepended to the path to each file being compiled for use in compilation time tracebacks, and is also compiled in to the byte-code file, where it will be used in tracebacks and other messages in cases where the source file does not exist at the time the byte-code file is executed.

If force is true, modules are re-compiled even if the timestamps are up to date.

If rx is given, its search method is called on the complete path to each file considered for compilation, and if it returns a true value, the file is skipped. This can be used to exclude files matching a regular expression, given as a re.Pattern object.

If quiet is False or 0 (the default), the filenames and other information are printed to standard out. Set to 1, only errors are printed. Set to 2, all output is suppressed.

If legacy is true, byte-code files are written to their legacy locations and names, which may overwrite byte-code files created by another version of Python. The default is to write files to their PEP 3147 locations and names, which allows byte-code files from multiple versions of Python to coexist.

optimize specifies the optimization level for the compiler. It is passed to the built-in compile() function. Accepts also a sequence of optimization levels which lead to multiple compilations of one .py file in one call.

The argument workers specifies how many workers are used to compile files in parallel. The default is to not use multiple workers. If the platform can’t use multiple workers and workers argument is given, then sequential compilation will be used as a fallback. If workers is 0, the number of cores in the system is used. If workers is lower than 0, a ValueError will be raised.

invalidation_mode should be a member of the py_compile.PycInvalidationMode enum and controls how the generated pycs are invalidated at runtime.

The stripdir, prependdir and limit_sl_dest arguments correspond to the -s, -p and -e options described above. They may be specified as str or os.PathLike.

If hardlink_dupes is true and two .pyc files with different optimization level have the same content, use hard links to consolidate duplicate files.

Changed in version 3.2: Added the legacy and optimize parameter.

Changed in version 3.5: Added the workers parameter.

Changed in version 3.5: quiet parameter was changed to a multilevel value.

Changed in version 3.5: The legacy parameter only writes out .pyc files, not .pyo files no matter what the value of optimize is.

Changed in version 3.6: Accepts a path-like object.

Changed in version 3.7: The invalidation_mode parameter was added.

Changed in version 3.7.2: The invalidation_mode parameter’s default value is updated to None.

Changed in version 3.8: Setting workers to 0 now chooses the optimal number of cores.

Changed in version 3.9: Added stripdir, prependdir, limit_sl_dest and hardlink_dupes arguments. Default value of maxlevels was changed from 10 to sys.getrecursionlimit()

compileall.compile_file(fullname, ddir=None, force=False, rx=None, quiet=0, legacy=False, optimize=-1, invalidation_mode=None, *, stripdir=None, prependdir=None, limit_sl_dest=None, hardlink_dupes=False)

Compile the file with path fullname. Return a true value if the file compiled successfully, and a false value otherwise.

If ddir is given, it is prepended to the path to the file being compiled for use in compilation time tracebacks, and is also compiled in to the byte-code file, where it will be used in tracebacks and other messages in cases where the source file does not exist at the time the byte-code file is executed.

If rx is given, its search method is passed the full path name to the file being compiled, and if it returns a true value, the file is not compiled and True is returned. This can be used to exclude files matching a regular expression, given as a re.Pattern object.

If quiet is False or 0 (the default), the filenames and other information are printed to standard out. Set to 1, only errors are printed. Set to 2, all output is suppressed.

If legacy is true, byte-code files are written to their legacy locations and names, which may overwrite byte-code files created by another version of Python. The default is to write files to their PEP 3147 locations and names, which allows byte-code files from multiple versions of Python to coexist.

optimize specifies the optimization level for the compiler. It is passed to the built-in compile() function. Accepts also a sequence of optimization levels which lead to multiple compilations of one .py file in one call.

invalidation_mode should be a member of the py_compile.PycInvalidationMode enum and controls how the generated pycs are invalidated at runtime.

The stripdir, prependdir and limit_sl_dest arguments correspond to the -s, -p and -e options described above. They may be specified as str or os.PathLike.

If hardlink_dupes is true and two .pyc files with different optimization level have the same content, use hard links to consolidate duplicate files.

Added in version 3.2.

Changed in version 3.5: quiet parameter was changed to a multilevel value.

Changed in version 3.5: The legacy parameter only writes out .pyc files, not .pyo files no matter what the value of optimize is.

Changed in version 3.7: The invalidation_mode parameter was added.

Changed in version 3.7.2: The invalidation_mode parameter’s default value is updated to None.

Changed in version 3.9: Added stripdir, prependdir, limit_sl_dest and hardlink_dupes arguments.

compileall.compile_path(skip_curdir=True, maxlevels=0, force=False, quiet=0, legacy=False, optimize=-1, invalidation_mode=None)

Byte-compile all the .py files found along sys.path. Return a true value if all the files compiled successfully, and a false value otherwise.

If skip_curdir is true (the default), the current directory is not included in the search. All other parameters are passed to the compile_dir() function. Note that unlike the other compile functions, maxlevels defaults to 0.

Changed in version 3.2: Added the legacy and optimize parameter.

Changed in version 3.5: quiet parameter was changed to a multilevel value.

Changed in version 3.5: The legacy parameter only writes out .pyc files, not .pyo files no matter what the value of optimize is.

Changed in version 3.7: The invalidation_mode parameter was added.

Changed in version 3.7.2: The invalidation_mode parameter’s default value is updated to None.

To force a recompile of all the .py files in the Lib/ subdirectory and all its subdirectories:

import compileall

compileall.compile_dir('Lib/', force=True)

# Perform same compilation, excluding files in .svn directories.
import re
compileall.compile_dir('Lib/', rx=re.compile(r'[/\\][.]svn'), force=True)

# pathlib.Path objects can also be used.
import pathlib
compileall.compile_dir(pathlib.Path('Lib/'), force=True)

See also

Module py_compile

Byte-compile a single source file.