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"""Routine to "compile" a .py file to a .pyc file.
This module has intimate knowledge of the format of .pyc files.
import enum
import importlib._bootstrap_external
import importlib.machinery
import importlib.util
import os
import os.path
import sys
import traceback
__all__ = ["compile", "main", "PyCompileError", "PycInvalidationMode"]
class PyCompileError(Exception):
"""Exception raised when an error occurs while attempting to
compile the file.
To raise this exception, use
raise PyCompileError(exc_type,exc_value,file[,msg])
exc_type: exception type to be used in error message
type name can be accesses as class variable
exc_value: exception value to be used in error message
can be accesses as class variable 'exc_value'
file: name of file being compiled to be used in error message
can be accesses as class variable 'file'
msg: string message to be written as error message
If no value is given, a default exception message will be
given, consistent with 'standard' py_compile output.
message (or default) can be accesses as class variable
def __init__(self, exc_type, exc_value, file, msg=''):
exc_type_name = exc_type.__name__
if exc_type is SyntaxError:
tbtext = ''.join(traceback.format_exception_only(
exc_type, exc_value))
errmsg = tbtext.replace('File "<string>"', 'File "%s"' % file)
errmsg = "Sorry: %s: %s" % (exc_type_name,exc_value)
Exception.__init__(self,msg or errmsg,exc_type_name,exc_value,file)
self.exc_type_name = exc_type_name
self.exc_value = exc_value
self.file = file
self.msg = msg or errmsg
def __str__(self):
return self.msg
class PycInvalidationMode(enum.Enum):
def _get_default_invalidation_mode():
if os.environ.get('SOURCE_DATE_EPOCH'):
return PycInvalidationMode.CHECKED_HASH
return PycInvalidationMode.TIMESTAMP
def compile(file, cfile=None, dfile=None, doraise=False, optimize=-1,
"""Byte-compile one Python source file to Python bytecode.
:param file: The source file name.
:param cfile: The target byte compiled file name. When not given, this
defaults to the PEP 3147/PEP 488 location.
:param dfile: Purported file name, i.e. the file name that shows up in
error messages. Defaults to the source file name.
:param doraise: Flag indicating whether or not an exception should be
raised when a compile error is found. If an exception occurs and this
flag is set to False, a string indicating the nature of the exception
will be printed, and the function will return to the caller. If an
exception occurs and this flag is set to True, a PyCompileError
exception will be raised.
:param optimize: The optimization level for the compiler. Valid values
are -1, 0, 1 and 2. A value of -1 means to use the optimization
level of the current interpreter, as given by -O command line options.
:param invalidation_mode:
:return: Path to the resulting byte compiled file.
Note that it isn't necessary to byte-compile Python modules for
execution efficiency -- Python itself byte-compiles a module when
it is loaded, and if it can, writes out the bytecode to the
corresponding .pyc file.
However, if a Python installation is shared between users, it is a
good idea to byte-compile all modules upon installation, since
other users may not be able to write in the source directories,
and thus they won't be able to write the .pyc file, and then
they would be byte-compiling every module each time it is loaded.
This can slow down program start-up considerably.
See for a script/module that uses this module to
byte-compile all installed files (or all files in selected
Do note that FileExistsError is raised if cfile ends up pointing at a
non-regular file or symlink. Because the compilation uses a file renaming,
the resulting file would be regular and thus not the same type of file as
it was previously.
if invalidation_mode is None:
invalidation_mode = _get_default_invalidation_mode()
if cfile is None:
if optimize >= 0:
optimization = optimize if optimize >= 1 else ''
cfile = importlib.util.cache_from_source(file,
cfile = importlib.util.cache_from_source(file)
if os.path.islink(cfile):
msg = ('{} is a symlink and will be changed into a regular file if '
'import writes a byte-compiled file to it')
raise FileExistsError(msg.format(cfile))
elif os.path.exists(cfile) and not os.path.isfile(cfile):
msg = ('{} is a non-regular file and will be changed into a regular '
'one if import writes a byte-compiled file to it')
raise FileExistsError(msg.format(cfile))
loader = importlib.machinery.SourceFileLoader('<py_compile>', file)
source_bytes = loader.get_data(file)
code = loader.source_to_code(source_bytes, dfile or file,
except Exception as err:
py_exc = PyCompileError(err.__class__, err, dfile or file)
if doraise:
raise py_exc
sys.stderr.write(py_exc.msg + '\n')
dirname = os.path.dirname(cfile)
if dirname:
except FileExistsError:
if invalidation_mode == PycInvalidationMode.TIMESTAMP:
source_stats = loader.path_stats(file)
bytecode = importlib._bootstrap_external._code_to_timestamp_pyc(
code, source_stats['mtime'], source_stats['size'])
source_hash = importlib.util.source_hash(source_bytes)
bytecode = importlib._bootstrap_external._code_to_hash_pyc(
(invalidation_mode == PycInvalidationMode.CHECKED_HASH),
mode = importlib._bootstrap_external._calc_mode(file)
importlib._bootstrap_external._write_atomic(cfile, bytecode, mode)
return cfile
def main(args=None):
"""Compile several source files.
The files named in 'args' (or on the command line, if 'args' is
not specified) are compiled and the resulting bytecode is cached
in the normal manner. This function does not search a directory
structure to locate source files; it only compiles files named
explicitly. If '-' is the only parameter in args, the list of
files is taken from standard input.
if args is None:
args = sys.argv[1:]
rv = 0
if args == ['-']:
while True:
filename = sys.stdin.readline()
if not filename:
filename = filename.rstrip('\n')
compile(filename, doraise=True)
except PyCompileError as error:
rv = 1
sys.stderr.write("%s\n" % error.msg)
except OSError as error:
rv = 1
sys.stderr.write("%s\n" % error)
for filename in args:
compile(filename, doraise=True)
except PyCompileError as error:
# return value to indicate at least one failure
rv = 1
sys.stderr.write("%s\n" % error.msg)
return rv
if __name__ == "__main__":