26.29 无some.py时"import some.pyc"

https://scz.617.cn/python/201309251607.txt

Q:

现有is_prime_pub.cpython-39.opt-2.pyc，没有is_prime_pub.py，此种情况可以直
接执行pyc

python is_prime_pub.cpython-39.opt-2.pyc 59

想进一步，在other.py中"import is_prime_pub"，并调用is_prime_pub中函数。

A: falsetru@stackoverflow 2013-09-25

参看

Import arbitrary python source file. (Python 3.3+)
https://stackoverflow.com/questions/19009932/import-arbitrary-python-source-file-python-3-3

有多种实现，用Python 3.9.0测试无误

--------------------------------------------------------------------------
import importlib.machinery
import importlib.util

#
# Load the compiled module from the .pyc file
#
loader          = importlib.machinery.SourcelessFileLoader( 'is_prime_pub', 'is_prime_pub.cpython-39.opt-2.pyc' )
spec            = importlib.util.spec_from_loader( loader.name, loader )
is_prime_pub    = importlib.util.module_from_spec( spec )
loader.exec_module( is_prime_pub )

#
# Call a method in the module
#
low_prime       = [2,3]
low_prime      += [x for x in range(5,2047,2) if is_prime_pub.rabin_miller_test(x,b=2,rounds=1)]
print( is_prime_pub.is_prime( 59, low_prime, 5 ) )
--------------------------------------------------------------------------
import importlib.machinery
import types

#
# Load the compiled module from the .pyc file
#
loader          = importlib.machinery.SourcelessFileLoader( 'is_prime_pub', 'is_prime_pub.cpython-39.opt-2.pyc' )
is_prime_pub    = types.ModuleType( loader.name )
loader.exec_module( is_prime_pub )

#
# Call a method in the module
#
low_prime       = [2,3]
low_prime      += [x for x in range(5,2047,2) if is_prime_pub.rabin_miller_test(x,b=2,rounds=1)]
print( is_prime_pub.is_prime( 59, low_prime, 5 ) )
--------------------------------------------------------------------------

用的是SourcelessFileLoader，不是SourceFileLoader，用后者时报错

ValueError: source code string cannot contain null bytes

无some.py直接加载some.pyc时，解释器会检查pyc首部"magic number"，必须匹配当
前解释器版本，否则报错，比如

ImportError: bad magic number in 'is_prime_pub': b'a\r\r\n'

--------------------------------------------------------------------------
import importlib.machinery

#
# Load the compiled module from the .pyc file
#
loader          = importlib.machinery.SourcelessFileLoader( 'is_prime_pub', 'is_prime_pub.cpython-39.opt-2.pyc' )
is_prime_pub    = loader.load_module()

#
# Call a method in the module
#
low_prime       = [2,3]
low_prime      += [x for x in range(5,2047,2) if is_prime_pub.rabin_miller_test(x,b=2,rounds=1)]
print( is_prime_pub.is_prime( 59, low_prime, 5 ) )
--------------------------------------------------------------------------

load_module()已废弃，不建议使用，会有警告，但在Python 3.9.0中仍可用

DeprecationWarning: the load_module() method is deprecated and slated for removal in Python 3.12; use exec_module() instead

--------------------------------------------------------------------------
import warnings

warnings.filterwarnings( "ignore", category=DeprecationWarning )

import sys, marshal, imp

def ManualLoadModule ( modulename, pycfile ) :
    header_size_list    = \
    [
        (16, (3, 7)),
        (12, (3, 3)),
        (8,  (0, 9, 2))
    ]
    header_size         = next( size for size, ver in header_size_list if sys.version_info >= ver )
    with open( pycfile, "rb" ) as f :
        f.read( header_size )
        co  = marshal.load( f )
    #
    # end of with
    #
    m                   = imp.new_module( modulename )
    exec( co, m.__dict__ )
    # print( dir( m ) )
    sys.modules[modulename] \
                        = m
#
# end of ManualLoadModule
#

ManualLoadModule( 'is_prime_pub', 'is_prime_pub.cpython-39.opt-2.pyc' )
import is_prime_pub

#
# Call a method in the module
#
low_prime       = [2,3]
low_prime      += [x for x in range(5,2047,2) if is_prime_pub.rabin_miller_test(x,b=2,rounds=1)]
print( is_prime_pub.is_prime( 59, low_prime, 5 ) )
--------------------------------------------------------------------------

warnings.filterwarnings是为了抑制如下警告

DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses