[英]Python submodule importing correctly in python 3.7 but not 3.6
I have a directory structure as follows:我的目录结构如下:
test/
__init__.py
m1/
__init__.py
f1.py
f2.py
test/__init__.py
is empty. test/__init__.py
是空的。
test/m1/__init__.py
contains a single line import test.m1.f1
. test/m1/__init__.py
包含一行import test.m1.f1
。
test/m1/f1.py
contains a single line import test.m1.f2 as f2
. test/m1/f1.py
包含一行import test.m1.f2 as f2
。
In python 3.7.6, I can do import test.m1
and everything works as expected.在 python 3.7.6 中,我可以执行
import test.m1
并且一切都按预期工作。 However, in python 3.6.9 when I try this I get the following error:但是,在 python 3.6.9 中,当我尝试此操作时,出现以下错误:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/scratch/test/m1/__init__.py", line 2, in <module>
import test.m1.f1
File "/home/scratch/test/m1/f1.py", line 1, in <module>
import test.m1.f2 as f2
AttributeError: module 'test' has no attribute 'm1'
This seems strange, because it does not error on the import test.m1.f1
, which is the first thing it encounters.这看起来很奇怪,因为它不会在
import test.m1.f1
上出错,这是它遇到的第一件事。 It errors on a subsequent import test.m1.f2 as f2
statement, claiming that test
has no m1
submodule.它在随后的
import test.m1.f2 as f2
语句中出错,声称test
没有m1
子模块。
import test.m1.f2 as f2
tries to access the m1
attribute of the test
module object, as part of the process of finding the object to bind to f2
. import test.m1.f2 as f2
尝试访问test
模块 object 的m1
属性,作为查找 object 以绑定到f2
的过程的一部分。 The m1
attribute won't be set until the test.m1
subpackage finishes initializing, which won't happen until the __init__.py
for test.m1
finishes executing.在 test.m1 子包完成初始化之前不会设置
m1
属性,直到test.m1
的__init__.py
完成执行test.m1
发生。
On Python 3.7 and up , if the attribute lookup fails, the import falls back to a sys.modules['test.m1.f2']
lookup to find test.m1.f2
.在 Python 3.7 及更高版本上,如果属性查找失败,导入将退回到
sys.modules['test.m1.f2']
查找以查找test.m1.f2
。 This fallback does not exist on 3.6, causing the observed discrepancy.这种回退在 3.6 上不存在,导致观察到的差异。
A similar fallback also exists for circular from
imports on Python 3.5 and up, though from. import f2
Python 3.5 及更高版本上
from
循环导入也存在类似的回退,尽管from. import f2
from. import f2
or from test.m1 import f2
wouldn't need the fallback. from. import f2
或from test.m1 import f2
不需要后备。 The from
import retrieves test.m1
straight from sys.modules
, so it only looks for the f2
attribute, and that attribute is present. from
import 直接从sys.modules
检索test.m1
,因此它只查找f2
属性,并且该属性存在。
This is not the answer explaining the how, but it explains how you can avoid the error.这不是解释如何的答案,但它解释了如何避免错误。 So useful for the ones wanting to write code that runs under 3.6 or earlier.
对于想要编写在 3.6 或更早版本下运行的代码的人来说非常有用。
Replace代替
import test1.m1.f2 as f2
with和
from test.m1 import f2
Or as @alaniwi pointed out或者正如@alaniwi 指出的那样
from . import f2
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