Python 包重名，导入系统包

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来源

之前使用PyQt5写的程序，但是目标系统没有，但是有PySide2/PySide6，因其授权更宽松。因为程序比较简单，那么，能不能一劳永逸？兼容各种Qt库版本呢？

思路

写一个自己的PyQt5包，处理兼容问题。这也就引出了当前的问题，在一个包里面，导入同名的系统包问题，或者叫“包重载”。

解决方案

这个问题耗了我2天时间

最终的解决方案是，使用修改包导入函数。参考官方importlib的导入包示例代码，但导入包时需要加前缀，并处理导入列表。

import os
import sys
import importlib.util__this_package_path__ = os.path.abspath(__package__ + '/..')__sys_path_without_this__ = [p for p in sys.path if not p.startswith(__this_package_path__)]def import_from_path(name,package=None,path=None,globals=None,locals=None,fromlist=(),rename=None
):"""An approximate implementation of import."""absolute_name = importlib.util.resolve_name(name, package)if rename:sys_module_name = '{}{}'.format(rename, absolute_name)else:sys_module_name = absolute_nametry:return sys.modules[sys_module_name]except KeyError:passhas_parent = Falseif '.' in absolute_name:has_parent = Trueparent_name, _, child_name = absolute_name.rpartition('.')parent_module = import_from_path(parent_name,package=package,path=path,globals=globals,locals=locals,fromlist=(),rename=rename,)path = parent_module.__spec__.submodule_search_locationsfor finder in sys.meta_path:spec = finder.find_spec(absolute_name, path)if spec is not None:breakelse:msg = f'No module named {absolute_name!r}'raise ModuleNotFoundError(msg, name=absolute_name)module = importlib.util.module_from_spec(spec)sys.modules[sys_module_name] = modulespec.loader.exec_module(module)if has_parent:setattr(parent_module, child_name, module)if len(fromlist) > 0:if '*' in fromlist:# is there an __all__?  if so respect itif "__all__" in module.__dict__:names = module.__dict__["__all__"]else:# otherwise we import all names that don't begin with _names = [x for x in module.__dict__ if not x.startswith("_")]else:names = fromlist# now drag them inif locals:locals.update({k: getattr(module, k) for k in names})if globals:globals.update({k: getattr(module, k) for k in names})return moduledef import_sys_module(name, package=None, globals=None, locals=None, fromlist=()):return import_from_path(name,package,__sys_path_without_this__,globals=globals,locals=locals,fromlist=fromlist,rename='Sys')

之后对于同名包，导入时使用import_sys_module函数导入

# PyQt5/__init__.py__qt_module__ = Nonetry:from PySide2 import *__qt_module__ = "PySide2"
except ImportError:try:from PySide6 import *__qt_module__ = "PySide6"except ImportError:try:import_sys_module('PyQt5',globals=globals(),locals=locals(),fromlist=('*',))__qt_module__ = "PyQt5"except ImportError:try:from PyQt6 import *__qt_module__ = "PyQt6"except ImportError:raise

其他模块

# PyQt5/QtCore/__init__.pyfrom .. import __qt_module__, import_sys_module
if __qt_module__ == 'PySide2':from PySide2.QtCore import *
elif __qt_module__ == 'PySide6':from PySide6.QtCore import *from PySide6.QtCore import Signal as pyqtSignal
elif __qt_module__ == 'PyQt5':import_sys_module('PyQt5.QtCore', globals=globals(), locals=locals(), fromlist=('*',))
elif __qt_module__ == 'PyQt6':from PyQt6.QtCore import *
else:raise ValueError('Can not handle this qt module: ', __qt_module__)

模块好多啊，那么能不能写个代码生成模块呢？

import os
import syscompat_qt_module_name = 'PyQt5'submodules = ['QtCore', 'QtGui', 'QtWidgets', 'sip']compat_qt_source_modules = ['PySide2', 'PySide6', 'PyQt5', 'PyQt6']# generate main module __init__.py codes
main_module_init_string = '''
import os
import sys
import importlib.util__this_package_path__ = os.path.abspath(__package__ + '/..')__sys_path_without_this__ = [p for p in sys.path if not p.startswith(__this_package_path__)]def import_from_path(name,package=None,path=None,globals=None,locals=None,fromlist=(),rename=None
):"""An approximate implementation of import."""absolute_name = importlib.util.resolve_name(name, package)if rename:sys_module_name = '{}{}'.format(rename, absolute_name)else:sys_module_name = absolute_nametry:return sys.modules[sys_module_name]except KeyError:passhas_parent = Falseif '.' in absolute_name:has_parent = Trueparent_name, _, child_name = absolute_name.rpartition('.')parent_module = import_from_path(parent_name,package=package,path=path,globals=globals,locals=locals,fromlist=(),rename=rename,)path = parent_module.__spec__.submodule_search_locationsfor finder in sys.meta_path:spec = finder.find_spec(absolute_name, path)if spec is not None:breakelse:msg = f'No module named {absolute_name!r}'raise ModuleNotFoundError(msg, name=absolute_name)module = importlib.util.module_from_spec(spec)sys.modules[sys_module_name] = modulespec.loader.exec_module(module)if has_parent:setattr(parent_module, child_name, module)if len(fromlist) > 0:if '*' in fromlist:# is there an __all__?  if so respect itif "__all__" in module.__dict__:names = module.__dict__["__all__"]else:# otherwise we import all names that don't begin with _names = [x for x in module.__dict__ if not x.startswith("_")]else:names = fromlist# now drag them inif locals:locals.update({k: getattr(module, k) for k in names})if globals:globals.update({k: getattr(module, k) for k in names})return moduledef import_sys_module(name, package=None, globals=None, locals=None, fromlist=()):return import_from_path(name,package,__sys_path_without_this__,globals=globals,locals=locals,fromlist=fromlist,rename='Sys')
'''main_module_init_string += '__qt_module__ = None\n'for i, sm in enumerate(compat_qt_source_modules):main_module_init_string += '    ' * i + 'try:\n'if not sm.startswith('PyQt5'):main_module_init_string += '    ' * i + '    from {} import *\n'.format(sm)else:main_module_init_string += '    ' * i + '    import_sys_module(\n'main_module_init_string += '    ' * i + '        \'PyQt5\',\n'main_module_init_string += '    ' * i + '        globals=globals(),\n'main_module_init_string += '    ' * i + '        locals=locals(),\n'main_module_init_string += '    ' * i + '        fromlist=(\'*\',)\n'main_module_init_string += '    ' * i + '    )\n'main_module_init_string += '    ' * i + '    __qt_module__ = "{}"\n'.format(sm)main_module_init_string += '    ' * i + 'except ImportError:\n'if i != len(compat_qt_source_modules) - 1:continueelse:main_module_init_string += '    ' * i + '    raise\n'print(main_module_init_string)
main_compat_qt_module_file = '{}/__init__.py'.format(compat_qt_module_name)os.makedirs(os.path.dirname(main_compat_qt_module_file), exist_ok=True)
with open(main_compat_qt_module_file, 'w') as fp:fp.write(main_module_init_string)# generate submodule __init__.py codes
for i, sm in enumerate(submodules):submodule_init_string = '\n'submodule_init_string += 'from {} import __qt_module__, import_sys_module\n'.format('.' * (len(sm.split('/')) + 1))for j, srm in enumerate(compat_qt_source_modules):submodule_init_string += '{} __qt_module__ == \'{}\':\n'.format('if' if j == 0 else 'elif', srm)if srm.startswith('PyQt5'):submodule_init_string += '    import_sys_module(\'{}.{}\',' \' globals=globals(), locals=locals(), fromlist=(' \'\'*\',))\n'.format(srm, sm)else:submodule_init_string += '    from {}.{} import *\n'.format(srm, sm)submodule_init_string += 'else:\n'submodule_init_string += '    raise ValueError(\'Can not handle this qt module: \', __qt_module__)\n'print(submodule_init_string)compat_qt_submodule_file = '{}/{}/__init__.py'.format(compat_qt_module_name, sm)os.makedirs(os.path.dirname(compat_qt_submodule_file), exist_ok=True)with open(compat_qt_submodule_file, 'w') as fp:fp.write(submodule_init_string)if __name__ == '__main__':pass