如何替换导入库中的导入?

Question

假设我们有三个文件:

library1.py:

SomeVariable = '1'

library2.py:

import library1
print(library1.SomeVariable)

library3.py:

SomeVariable = '2'

我的目标是"改变"在library2.py中导入Library1(不只有1个变量)，因此结果输出将为'2'(换句话说，将library2.py中library1的缓存替换为library3)

Answer 1

警告:此方法非常hacky，并且您可能可能会破坏东西。

---

假设我们有这个library1.py:

var1 = 100
var2 = 'never gonna give you up'
a = 3.1415926

并且，我们想用overwrite.py覆盖它:

var1 = -9999
var2 = 'never gonna let you down'
a = 2.71828

---

如果我们进入shell，我们可以看到一个模块有一个__dict__属性，它包含了它内部的所有内容。

>>> import library1
>>> library1.__dict__
# NOTE: This also contains a bunch of python's variables, including their builtins, magic things like `__name__`, etc
# I cut them out for simplicity
{'var1': 100, 'var2': 'never gonna give you up', 'a': 3.1415926}

这很好，因为我们可以使用它来访问属性，而不需要真正访问它们:

>>> import library1
>>> library1.__dict__['a'] = 'never gonna run around and desert you'
>>> library1.a
'never gonna run around and desert you'
>>> library1.__dict__['this_variable_wasnt_even_defined'] = 'never gonna make you cry'
>>> library1.this_variable_wasnt_even_defined
'never gonna make you cry'

---

我们不想覆盖任何魔法(以两个下划线开始和结束)属性，所以:

>>> def is_magic(name: str) -> bool:
...     return name[0] == '_' and name[1] == '_' and name[-1] == '_' and name[-2] == '_'
>>> is_magic('not_very_magic_variable')
False
>>> is_magic('__name__')
True
>>> is_magic('__init__')
True

我们也不想覆盖任何内置函数:

>>> def is_builtin(obj: object) -> bool:
...     builtin_type = type(print)
...     return obj.__class__ is builtin_type
... 
>>> is_builtin(print)
True
>>> is_builtin(open)
True

---

这是所有这些都聚集在一起的地方。

我们使用library3中的值来覆盖library1中的__dict__。

>>> from utils import is_builtin, is_magic
>>> import library1
>>> import overwrite
>>> 
>>> for key, value in overwrite.__dict__.items():
...     if is_magic(key):
...         continue
...     if is_builtin(value):
...         continue
...     # otherwise, we have something to overwrite
...     library1.__dict__[key] = value
...     print(f'I have overwritten {key} with {value}')
... 
I have overwritten var1 with -9999
I have overwritten var2 with never gonna let you down
I have overwritten a with 2.71828

您可以看到library1已被覆盖:

# ...
>>> library1.var1
-9999
>>> library1.var2
'never gonna let you down'
>>> library1.a
2.71828

Answer 2

我找到了一种方法:

import library1,library2,library3
import importlib
for i in library3.__dict__.keys():
library1.__dict__[i] = library3.__dict__[i]
library2 = importlib.reload(library2)

Answer 3

你可以使用copy

import copy
b = copy.copy(lib1.a)
...
print(lib2.b)