Python：如何让file2中的动态导入传递回调用它的file1？

问题背景 #

我编写了一个工具，可自动安装依赖并重启脚本，无需用户排查错误手动安装。理想用法如下：

# file1.py
from file2 import import_and_install
succ = import_and_install("numpy") # 导入numpy
succ |= import_and_install("cv2", "opencv-python") # 导入cv2（对应包名opencv-python）
succ |= import_and_install("openpyxl", alias="xl") # 导入openpyxl并命名为xl

但实际调用后发现，file2中函数执行的导入无法传递回file1，只能改用以下繁琐的写法：

# alternate_file1.py
try:
    print("IMPORT LIBS")
    print("")
    import numpy
    import cv2
    import openpyxl as xl
except:
    succ = import_and_install("numpy") # 导入numpy
succ |= import_and_install("cv2", "opencv-python") # 导入cv2
succ |= import_and_install("openpyxl", alias="xl") # 导入openpyxl
if not succ == 4096:
    exit(1)

直接把file2的代码复制到file1里就能正常工作，但频繁复制代码太麻烦。请问如何让动态导入的结果传递回原文件file1？

原file2.py代码如下：

# file2.py
import os
import sys
import importlib
import subprocess
import traceback

def try_import(import_name, alt_install_name=None, from_pkg=None, alias=None):
    succ = 4096
    # 支持不同的导入策略，导入失败时尝试安装
    try:
        if from_pkg is None:
            to_import = import_name
        elif not (from_pkg is None):
            to_import = from_pkg
        else:
            raise AttributeError("Not a valid package")
    
        import_entry = importlib.import_module(to_import)
        if not (from_pkg is None):
            import_entry = import_entry.__dict__[import_name]
        
        print(import_entry)
        print(to_import)
        if(not (alias is None)):
            globals()[alias] = import_entry
        else:
            globals()[import_name] = import_entry

    except AttributeError:
        print("Not a valid package")
        succ |= 1
    except ImportError:
        print("can't find the " + to_import + " module.")
        succ |= 2
    
    if not (alt_install_name is None):
        to_install = alt_install_name
    else:
        to_install = to_import
        
    return succ, to_install
    
def try_install(to_install):
    # 导入失败时询问用户是否安装缺失包
    succ = 4096
    should_install = input("Would you like to install? (y/n): ")
    if should_install.lower() in ('y', 'yes'):
        try:
            ret = subprocess.check_call([sys.executable, "-m", "pip", 'install', to_install])
        except ChildProcessError:
            print("Failed to install package with return code " + str(ret) + ". Try again manually")
            succ |= 4
        else:
            print("Install attempted.")
            restart_script()

    else:
        print("You can't run the script until you install the package")
        succ |= 8
        
    return succ

def restart_script():
        print("Restarting script. If restart fails try again manually.")
        print('\a')
        if not (os.name == 'nt'):
            os.execl(sys.executable, 'python', traceback.extract_stack()[0].filename, *sys.argv[1:])
        else:
            p = subprocess.call([sys.executable, os.path.realpath(traceback.extract_stack()[0].filename), *sys.argv], shell=True, start_new_session=True)
            sys.exit(0)

def import_and_install(import_name, alt_name=None, from_pkg=None, alias=None):
    succ, to_install = try_import(import_name, alt_name, from_pkg, alias)
    
    if succ == (4096 | 2):
        succ |= try_install(to_install)

    return succ

解决方案 #

问题出在try_import函数中使用的globals()——它指向的是file2.py模块自身的全局命名空间，而非调用者file1.py的。要解决这个问题，需要获取调用者的全局命名空间并将导入的模块绑定到那里。

修改后的file2.py代码 #

# file2.py
import os
import sys
import importlib
import subprocess
import traceback
import inspect  # 新增：用于获取调用者栈帧

def try_import(import_name, alt_install_name=None, from_pkg=None, alias=None):
    succ = 4096
    # 获取调用者的全局命名空间
    caller_globals = inspect.currentframe().f_back.f_globals
    
    try:
        if from_pkg is None:
            to_import = import_name
        else:
            to_import = from_pkg
    
        import_entry = importlib.import_module(to_import)
        if from_pkg is not None:
            import_entry = import_entry.__dict__[import_name]
        
        print(import_entry)
        print(to_import)
        # 将导入的对象绑定到调用者的全局命名空间
        if alias is not None:
            caller_globals[alias] = import_entry
        else:
            caller_globals[import_name] = import_entry

    except AttributeError:
        print("无效的包")
        succ |= 1
    except ImportError:
        print(f"找不到模块 {to_import}")
        succ |= 2
    
    to_install = alt_install_name if alt_install_name is not None else to_import
        
    return succ, to_install
    
def try_install(to_install):
    succ = 4096
    should_install = input("是否安装该包？(y/n): ")
    if should_install.lower() in ('y', 'yes'):
        try:
            ret = subprocess.check_call([sys.executable, "-m", "pip", 'install', to_install])
        except ChildProcessError as e:
            print(f"安装失败，返回码 {e.returncode}。请手动重试")
            succ |= 4
        else:
            print("安装已尝试，正在重启脚本")
            restart_script()

    else:
        print("必须安装该包才能运行脚本")
        succ |= 8
        
    return succ

def restart_script():
        print("正在重启脚本。如果重启失败请手动重试")
        print('\a')
        if os.name != 'nt':
            os.execl(sys.executable, 'python', traceback.extract_stack()[0].filename, *sys.argv[1:])
        else:
            p = subprocess.call([sys.executable, os.path.realpath(traceback.extract_stack()[0].filename), *sys.argv], shell=True, start_new_session=True)
            sys.exit(0)

def import_and_install(import_name, alt_name=None, from_pkg=None, alias=None):
    succ, to_install = try_import(import_name, alt_name, from_pkg, alias)
    
    if succ == (4096 | 2):
        succ |= try_install(to_install)

    return succ

修改说明 #

1. 新增inspect模块导入：用于获取调用者的栈帧信息，从而拿到调用脚本的全局命名空间。
2. 替换globals()为caller_globals：inspect.currentframe().f_back.f_globals指向调用try_import函数的脚本（即file1.py）的全局变量字典，这样导入的模块或别名就会被添加到调用者的全局命名空间中，在file1里直接就能使用。
3. 优化部分提示文本：将英文提示改为中文，提升可读性。

验证理想用法 #

修改后，最初的file1.py代码可以正常工作：

# file1.py
from file2 import import_and_install
succ = import_and_install("numpy") # 导入numpy
succ |= import_and_install("cv2", "opencv-python") # 导入cv2
succ |= import_and_install("openpyxl", alias="xl") # 导入openpyxl并命名为xl

# 现在可以直接使用这些模块
print(numpy.__version__)
print(cv2.__version__)
print(xl.__version__)

内容的提问来源于stack exchange，提问作者Painguy