Python：如何从依赖于该包中其他函数的包中导入函数？

Question

考虑以下场景：

test_setup/
├── __init__.py
├── helper.py
└── main.py

helper.py 是：

def helper_func():
    print('helping')

main.py 是：

from helper import helper_func

def main_func():
    helper_func()

if __name__ == '__main__':
    main_func()

__init__.py 是：

from .main import main_func

我希望能够做两件事：

1.从包中运行main。这行得通。

2.import main_func 在此包外使用。这行不通。从test_setup的父目录调用时， from test_setup import main_func 产量：

In [1]: from test_setup import main_func
---------------------------------------------------------------------------
ModuleNotFoundError                       Traceback (most recent call last)
<ipython-input-1-c395483f58c8> in <module>
----> 1 from test_setup import main_func

~/PycharmProjects/test_setup/__init__.py in <module>
      1 #from .helper import helper_func
----> 2 from .main import main_func

~/PycharmProjects/test_setup/main.py in <module>
----> 1 from helper import helper_func
      2 
      3 def main_func():
      4     helper_func()
      5 

ModuleNotFoundError: No module named 'helper'

如果我将 main.py 中的第一行更改为相对导入 from .helper import helper_func 可以工作，但是当我尝试从包内运行时失败（上面的目标 1）产生：

Traceback (most recent call last):
  File "/Users/xxx/PycharmProjects/test_setup/main.py", line 1, in <module>
    from .helper import helper_func
ImportError: attempted relative import with no known parent package

这里发生了什么，我该如何解决问题以实现目标 1 和 2？尝试在__init__.py 中导入helper_func 也无济于事。 以下也失败了：

In [1]: from test_setup.main import main_func
---------------------------------------------------------------------------
ModuleNotFoundError                       Traceback (most recent call last)
<ipython-input-1-764832db473f> in <module>
----> 1 from test_setup.main import main_func

~/PycharmProjects/test_setup/__init__.py in <module>
----> 1 from .main import main_func

~/PycharmProjects/test_setup/main.py in <module>
----> 1 from helper import helper_func
      2 
      3 def main_func():
      4     helper_func()
      5 

ModuleNotFoundError: No module named 'helper'

Answer 1

直接导入函数应该是：from test_setup.main import main_func。但是，您可以从模块中使用它。

import test_setup

test_setup.main_func()

在编辑时，您错过了 from .helper import helper_func 上的 . 以指示相对导入。

进一步查看目标 1 问题和this great post you should read，Guido 本人建议不要在模块内运行脚本，而不是作为模块运行。

import docs 说：

请注意，相对导入基于当前模块的名称。由于主模块的名称始终为“ma​​in”，因此用作 Python 应用程序主模块的模块必须始终使用绝对导入。

这意味着脚本（你可以独立于包运行的东西）不应该在可能的情况下从内部运行。如果需要保留当前结构，可以使用 python -m test_setup.main 将 main.py 文件作为模块运行，这将与相对导入一起使用。

另一种选择是将父文件夹添加到 test_setup 文件夹到 PYTHONPATH，这将允许从任何地方进行绝对导入，例如 test_setup.main.main_func，尽管有 good threads 建议您在构建包时应该使用 proper development tools。

Answer 2

不知道您使用的是哪个版本，但这可能会对您有所帮助...

__init__.py:

# 1. run main from within the package

# Python2
'''
>>> from main import main_func
main: from helper import helper_func
>>> main_func()
helping
'''

# Python3
'''
>>> from main import main_func
main: from helper import helper_func
>>> main_func()
helping
'''

# XXX: Notice that both of the above are the same
# However, note the differences below

# 2. import main_func for use outside this package

# Python2
'''
>>> from test_setup import main_func
test_setup.main: from helper import helper_func
test_setup: from main import main_func
>>> main_func()
helping
'''

# Python3
'''
>>> from test_setup import main_func
# Failed
ImportError:0 No module named 'main' in module test_setup
ImportError:0 No module named 'helper' in module test_setup.main
# Succeeded
test_setup.main: from .helper import helper_func
test_setup: from .main import main_func
>>> main_func()
helping
'''

try:
    from main import main_func
    print("%s: from main import main_func"%(__name__))
except ImportError as exc:
    print("ImportError:0 %s in module %s"%(exc,__name__))
    try:
        from .main import main_func
        print("%s: from .main import main_func"%(__name__))
    except ImportError as exc:
        print("ImportError:1 %s in module %s"%(exc,__name__))
        from test_setup.main import main_func
        print("%s: from test_setup.main import main_func"%(__name__))

main.py:

try:
    from helper import helper_func
    print("%s: from helper import helper_func"%(__name__))
except ImportError as exc:
    print("ImportError:0 %s in module %s"%(exc,__name__))
    try:
        from .helper import helper_func
        print("%s: from .helper import helper_func"%(__name__))
    except ImportError as exc:
        print("ImportError:1 %s in module %s"%(exc,__name__))
        from test_setup.helper import helper_func
        print("%s from test_setup.helper import helper_func"%(__name__))


def main_func():
    helper_func()

if __name__ == '__main__':
    main_func()

为澄清而编辑：

__init__.py:

"""Init for main module"""

print("__init__.__doc__ = %s"%(__doc__))

# -----------------------------------------------------------------------------
from os import path
import sys

print("sys.executable = %s"%(sys.executable))
print("sys.argv[0] = %s"%(sys.argv[0]))

main_prg_path = path.abspath(path.dirname(__file__))
print("main_prg_path = %s"%(main_prg_path))

if getattr(sys, 'frozen', False):
    # When being bundled by pyinstaller, paths are different
    print("Running as pyinstaller bundle!", sys.argv[0])
    main_prg_path = path.abspath(path.dirname(sys.argv[0]))

sys.path.append(main_prg_path)
print("main_prg_path = %s"%(main_prg_path))
# Append other directories needed for main program
#sys.path.append(os.path.join(main_prg_path, 'utils'))

# -----------------------------------------------------------------------------
from main import main_func

main.py:

"""Main module"""

print("main.__doc__ = %s"%(__doc__))

# -----------------------------------------------------------------------------
# Running in python
# inside:  from main import main_func
# outside: from test_setup import main_func

# Running in terminal
# inside:  python -m main
# outside: python -m test_setup/main
# -----------------------------------------------------------------------------
from os import path
import sys

print("sys.executable = %s"%(sys.executable))
print("sys.argv[0] = %s"%(sys.argv[0]))

main_prg_path = path.abspath(path.dirname(__file__))
print("main_prg_path = %s"%(main_prg_path))

if getattr(sys, 'frozen', False):
    # When being bundled by pyinstaller, paths are different
    print("Running as pyinstaller bundle!", sys.argv[0])
    main_prg_path = path.abspath(path.dirname(sys.argv[0]))

sys.path.append(main_prg_path)
print("main_prg_path = %s"%(main_prg_path))
# Append other directories needed for main program
#sys.path.append(os.path.join(main_prg_path, 'utils'))

# -----------------------------------------------------------------------------
from helper import helper_func


def main_func():
    helper_func()

# -----------------------------------------------------------------------------
if __name__ == '__main__':
    print("running as main: %s"%(__name__))
    main_func()
else:
    print("running as file: %s"%(__file__))
    main_func()

helper.py:

"""Helper module"""

print("helper.__doc__ = %s"%(__doc__))

__author__ = "Your Name"
__author_email__ = "Your Email"
__version__ = "0.0.1"
__date__ = "24 Jan 2021"

def helper_func():
    print("Author = %s\nEmail = %s\nVersion = %s\nDate = %s"%(
        __author__, __author_email__, __version__, __date__))

@rhz 编辑：添加更改以显示正在发生的事情和sys.path.append 的简单用法示例