循环导入以修复 pylint 中的 R0401 错误

Question

针对 NLTK 包的某个特定文件，例如，Pylint 在 R0401 错误代码下抱怨循环导入。

nltk/nltk/ccg/lexicon.py:1: [R0401(cyclic-import), ] Cyclic import (nltk -> nltk.internals)
nltk/nltk/ccg/lexicon.py:1: [R0401(cyclic-import), ] Cyclic import (nltk.corpus -> nltk.tokenize -> nltk.tokenize.punkt -> nltk.probability)
nltk/nltk/ccg/lexicon.py:1: [R0401(cyclic-import), ] Cyclic import (nltk.corpus -> nltk.tokenize -> nltk.tokenize.texttiling)
nltk/nltk/ccg/lexicon.py:1: [R0401(cyclic-import), ] Cyclic import (nltk.draw.tree -> nltk.tree)
nltk/nltk/ccg/lexicon.py:1: [R0401(cyclic-import), ] Cyclic import (nltk.tree -> nltk.treeprettyprinter)
nltk/nltk/ccg/lexicon.py:1: [R0401(cyclic-import), ] Cyclic import (nltk.grammar -> nltk.parse.pchart)
nltk/nltk/ccg/lexicon.py:1: [R0401(cyclic-import), ] Cyclic import (nltk.stem -> nltk.stem.porter)
nltk/nltk/ccg/lexicon.py:1: [R0401(cyclic-import), ] Cyclic import (nltk.classify.maxent -> nltk.classify.tadm)

完整的列表在https://github.com/nltk/nltk/issues/2113上。但是看一下导入：

from __future__ import unicode_literals from 

import re
from collections import defaultdict

from nltk.ccg.api import PrimitiveCategory, Direction, CCGVar, FunctionalCategory
from nltk.compat import python_2_unicode_compatible
from nltk.internals import deprecated

from nltk.sem.logic import *

但是看一下 nltk.internals 的https://github.com/nltk/nltk/blob/develop/nltk/internals.py，没有任何指向 nltk.ccg.lexicon 的循环导入：

from __future__ import print_function

import subprocess
import os
import fnmatch
import re
import warnings
import textwrap
import types
import sys
import stat
import locale

# Use the c version of ElementTree, which is faster, if possible:
try:
    from xml.etree import cElementTree as ElementTree
except ImportError:
    from xml.etree import ElementTree

from six import string_types

from nltk import __file__
from nltk import compat

什么是 R0401(cyclic-import) 错误信息？

查看 nltk.ccg.lexicon.py 和 nltk.internals.py，没有循环引用的导入，那么该问题应如何解决。

- alvas

Answer 1

我不确定为什么pylint会在nltk/nltk/ccg/lexicon.py文件中报告这些问题，但是循环导入本身可以在错误消息右侧看到。

针对第一个错误：Cyclic import (nltk -> nltk.internals)：根__init__.py从nltk.internals进行了导入，而internals.py从包的根目录进行了导入，这显然是一个循环导入。

- Mikhail Burshteyn