[英]from A.B import X using __import__?
Let's say A is a package directory, B is a module within the directory, and X is a function or variable written in B. How can I import X using the __import__()
syntax? 假设A是包目录,B是目录中的模块,X是用B编写的函数或变量。如何使用__import__()
语法导入X? Using scipy as an example: 以scipy为例:
What I want: 我想要的是:
from scipy.constants.constants import yotta
What doesn't work: 什么行不通:
>>> __import__("yotta", fromlist="scipy.constants.constants")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named yotta
>>> __import__("yotta", fromlist=["scipy.constants.constants"])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named yotta
>>> __import__("yotta", fromlist=["scipy","constants","constants"])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named yotta
>>> __import__("scipy.constants.constants.yotta", fromlist=["scipy.constants.constats"])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named yotta
Any suggestions would be much appreciated. 任何建议将不胜感激。
The python import statement performs two tasks: loading the module and makeing it available in the namespace. python import语句执行两个任务:加载模块并使其在命名空间中可用。
import foo.bar.baz
will provide the name foo
in the namespace, not baz
, so __import__
will give you foo
将在命名空间中提供名称foo
,而不是baz
,所以__import__
会给你foo
foo = __import__('foo.bar.baz')
On the other hand 另一方面
from foo.bar.baz import a, b
does not make a module available, but what the import statement needs to perform the assignmaents is baz. 没有使模块可用,但import语句执行assignmaents需要的是baz。 this corresponds to 这对应于
_tmp_baz = __import__('foo.bar.baz', fromlist=['a', 'b'])
a = _tmp_baz.a
b = _tmp_baz.b
without making the temporary visible, of course. 当然,没有使临时可见。
the __import__
function does not enforce the presence of a
and b
, so when you want baz
you can just give anything in the fromlist argument to put __import__
in the "from input" mode. 该__import__
功能并不强制存在a
和b
,所以当你想baz
你可以给在fromlist里争论什么把__import__
在“从输入”模式。
So the solution is the following. 所以解决方案如下。 Assuming 'yotta' is given as a string variable, I have used getattr
for attribute access. 假设'yotta'作为字符串变量给出,我使用getattr
进行属性访问。
yotta = getattr(__import__('scipy.constants.constants',
fromlist=['yotta']),
'yotta')
__import__("scipy.constants.constants", fromlist=["yotta"])
The argument fromlist
is equivalent to the right hand side of from LHS import RHS
. fromlist
的参数等同from LHS import RHS
的右侧 。
__import__(name[, globals[, locals[, fromlist[, level]]]])
[...] [...]
The
fromlist
gives the names of objects or submodules that should be imported from the module given byname
.fromlist
给出了应该从name
给出的模块导入的对象或子模块的name
。[...] [...]
On the other hand, the statement
from spam.ham import eggs, sausage as saus
results in 另一方面,from spam.ham import eggs, sausage as saus
的声明from spam.ham import eggs, sausage as saus
结果_temp = __import__('spam.ham', globals(), locals(), ['eggs', 'sausage'], -1) eggs = _temp.eggs saus = _temp.sausage
(Emphasis mine.) (强调我的。)
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