问题描述
假设我有一个文件script.py位于path = "foo/bar/script.py"。我正在寻找Python中通过函数script.py在我的主要Python程序中以编程方式执行execute_script()的方法。但是，我有一些要求似乎阻止我采用涉及importlib或exec()的幼稚方法：
-
script.py应该在“新鲜”的Python环境中执行，就像它通过$ python script.py运行一样。也就是说，应该相应地设置所有相关的全局变量，例如__name__，__file__，sys.modules，sys.path和工作目录，并且应从我的主程序中泄漏尽可能少的信息进入文件的执行。 （不过，如果script.py可以通过inspect模块发现不是直接通过$ python script.py执行的，那就没关系。） -
我需要访问执行结果，即
execute_script()应该返回script.py给定的模块及其所有变量，函数和类。 （这可防止在子进程中启动新的Python解释器。） -
execute_script()必须在内部使用open()来读入script.py。这样一来，我就可以在单元测试期间使用pyfakefs包来模拟文件系统。 （这避免了涉及importlib的简单解决方案。） -
execute_script()不得（永久）修改我的主程序中的任何全局状态，例如sys.path或sys.modules。 -
如果可能，
script.py应该不会影响我的主程序的全局状态。 （至少它应该不会影响我的主程序中的sys.path和sys.modules。） -
我需要能够修改
sys.path看到的script.py。execute_function()因此应接受系统路径的可选列表作为参数。 -
该解决方案应尽可能地面向未来，并且不依赖于Python解释器的实现细节。
对于任何想法，我将不胜感激！
解决方法
我刚发现exec()也接受代码对象（例如可以从compile()获得）的事实，并提出了一种似乎可以满足几乎所有要求的方法。之所以“接近”，是因为除了sys.path和sys.modules之外，脚本仍然可以影响主程序的全局状态。此外，还可以查看在调用execute_script()之前导入的所有模块。暂时我对此很满意。
这是包含测试的完整代码：
import os
import sys
from typing import List
module = os.__class__
def create_module(name: str,file: str) -> module:
mod = module(name)
# Instances of `module` automatically come with properties __doc__,# __loader__,__name__,__package__ and __spec___. Let's add some
# more properties that main modules usually come with:
mod.__annotations__ = {}
# __builtins__ doesn't show up in dir() but still exists
mod.__builtins__ = __builtins__
mod.__file__ = file
return mod
def exec_script(path: str,working_dir: str,syspath: List[str] = None) -> module:
"""
Execute a Python script as if it were executed using `$ python
<path>` from inside the given working directory. `path` can either
be an absolute path or a path relative to `working_dir`.
If `syspath` is provided,a copy of it will be used as `sys.path`
during execution. Otherwise,`sys.path` will be set to
`sys.path[1:]` which – assuming that `sys.path` has not been
modified so far – removes the working directory from the time when
the current Python program was started. Either way,the directory
containing the script at `path` will always be added at position 0
in `sys.path` afterwards,so as to simulate execution via `$ python
<path>`.
"""
if os.path.isabs(path):
abs_path = path
else:
abs_path = os.path.join(os.path.abspath(working_dir),path)
with open(abs_path,"r") as f:
source = f.read()
if sys.version_info < (3,9):
# Prior to Python 3.9,the __file__ variable inside the main
# module always contained the path exactly as it was given to `$
# python`,no matter whether it is relative or absolute and/or a
# symlink.
the__file__ = path
else:
# Starting from Python 3.9,__file__ inside the main module is
# always an absolute path.
the__file__ = abs_path
# The filename passed to compile() will be used in stack traces and
# error messages. It normally it agrees with __file__.
code = compile(source,filename=the__file__,mode="exec")
sysmodules_backup = sys.modules
sys.modules = sys.modules.copy()
the_module = create_module(name="__main__",file=the__file__)
sys.modules["__main__"] = the_module
# According to
# https://docs.python.org/3/tutorial/modules.html#the-module-search-path
# if the script is a symlink,the symlink is followed before the
# directory containing the script is added to sys.path.
if os.path.islink(abs_path):
sys_path_dir = os.path.dirname(os.readlink(abs_path))
else:
sys_path_dir = os.path.dirname(abs_path)
if syspath is None:
syspath = sys.path[1:]
syspath_backup = sys.path
sys.path = [
sys_path_dir
] + syspath # This will automatically create a copy of syspath
cwd_backup = os.getcwd()
os.chdir(working_dir)
# For code inside a module,global and local variables are given by
# the *same* dictionary
globals_ = the_module.__dict__
locals_ = the_module.__dict__
exec(code,globals_,locals_)
os.chdir(cwd_backup)
sys.modules = sysmodules_backup
sys.path = syspath_backup
return the_module
#################
##### Tests #####
#################
# Make sure to install pyfakefs via pip!
import unittest
import pyfakefs
class Test_exec_script(pyfakefs.fake_filesystem_unittest.TestCase):
def setUp(self):
self.setUpPyfakefs()
self.fs.create_file(
"/folder/script.py",contents="\n".join(
[
"import os","import sys","","cwd = os.getcwd()","sysmodules = sys.modules","syspath = sys.path","sys.modules['test_module'] = 'bar'","sys.path.append('/some/path')",]
),)
self.fs.create_symlink("/folder2/symlink.py","/folder/script.py")
#
# __name__
#
def test__name__is_set_correctly(self):
module = exec_script("script.py","/folder")
assert module.__name__ == "__main__"
#
# __file__
#
def test_relative_path_works_and__file__shows_it(self):
module = exec_script("script.py","/folder")
assert module.__file__ == "script.py"
def test_absolute_path_works_and__file__shows_it(self):
module = exec_script("/folder/script.py","/folder")
assert module.__file__ == "/folder/script.py"
def test__file__doesnt_follow_symlink(self):
module = exec_script("symlink.py","/folder2")
assert module.__file__ == "symlink.py"
#
# working dir
#
def test_working_directory_is_set_and_reset_correctly(self):
os.chdir("/")
module = exec_script("/folder/script.py","/folder")
assert module.cwd == "/folder"
assert os.getcwd() == "/"
#
# sys.modules
#
def test__main__module_is_set_correctly(self):
module = exec_script("/folder/script.py","/folder")
assert module.sysmodules["__main__"] == module
def test_script_cannot_modify_our_sys_modules(self):
sysmodules_backup = sys.modules.copy()
exec_script("/folder/script.py","/folder")
assert sys.modules == sysmodules_backup
#
# sys.path
#
def test_script_cannot_modify_our_sys_path(self):
syspath_backup = sys.path.copy()
exec_script("/folder/script.py","/folder")
assert sys.path == syspath_backup
def test_sys_path_is_set_up_correctly(self):
syspath_backup = sys.path[:]
module = exec_script("/folder/script.py","/folder")
assert module.syspath[0] == "/folder"
assert module.syspath[1:] == syspath_backup[1:] + ["/some/path"]
def test_symlink_is_followed_before_adding_base_dir_to_sys_path(self):
module = exec_script("symlink.py","/folder2")
assert module.syspath[0] == "/folder"
if __name__ == "__main__":
unittest.main()