如何仅修改runner.py实现Python3全局作用域跨文件夹函数调用

环境与目录结构 #

开发环境：Linux Mint 21 + Python 3.x
项目目录结构：

└── main_dir/
    ├── all_files_dir/
    │   ├── a_files_dir/
    │   │   └── file_a.py
    │   ├── b_files_dir/
    │   │   └── file_b.py
    │   └── c_files_dir/
    │       └── file_c.py
    └── runner.py

各文件内容 #

• file_a.py

def function_a():
    print("a ran")
    return "a return value "

• file_b.py

def function_b():
    print("b ran")
    return "b return value "

• file_c.py

def function_c():
    print("this function STARTS running!!!")
    result_of_function_a = a()
    result_of_function_b = b()
    results_of_both_functions = result_of_function_a + result_of_function_b
    print("results_of_both_functions", results_of_both_functions)

• 原runner.py

from all_files_dir.a_files_dir.file_a import function_a as a
a() # This Works!

from all_files_dir.b_files_dir.file_b import function_b as b
b() # This Works!

from all_files_dir.c_files_dir.file_c import function_c as c
c() # This STARTS working and prints 'this function STARTS running!!!'
# This FAILS eventually!!!

报错信息 #

运行原runner.py后报错：

a ran
b ran
this function STARTS running!!!
Traceback (most recent call last):
  File ".../main_dir/runner.py", line 8, in <module>
    c() # This STARTS working and prints 'this function STARTS running!!!'
  File ".../main_dir/all_files_dir/c_files_dir/file_c.py", line 3, in function_c
    result_of_function_a = a()
NameError: name 'a' is not defined

需求说明 #

不修改all_files_dir目录下的任何文件，仅修改runner.py，将function_a()导入为a()、function_b()导入为b()、function_c()导入为c()，使三者处于可互相调用的全局作用域。

解决方案 #

核心思路是将runner.py中导入的a和b注入到file_c模块的全局命名空间中，这样function_c运行时就能找到这两个函数。修改后的runner.py如下：

# 先导入a和b
from all_files_dir.a_files_dir.file_a import function_a as a
from all_files_dir.b_files_dir.file_b import function_b as b

# 导入file_c模块（而非直接导入function_c）
import all_files_dir.c_files_dir.file_c as file_c_module
# 将a、b注入到file_c模块的全局变量中
file_c_module.a = a
file_c_module.b = b

# 再将function_c导入为c
from all_files_dir.c_files_dir.file_c import function_c as c

# 测试调用
a()
b()
c()

运行修改后的runner.py，即可正常输出：

a ran
b ran
a ran
b ran
this function STARTS running!!!
results_of_both_functions a return value b return value 

内容的提问来源于stack exchange，提问作者Pavel Bogdanov