How to replace imports in imported library?-CodePudding

Suppose, we have 3 files:

library1.py:

SomeVariable = '1'

library2.py:

import library1
print(library1.SomeVariable)

library3.py:

SomeVariable = '2'

my goal is to "change" library1 import(not only 1 variable) in library2.py so result output will be '2' (in other words,replace cache of library1 in library2.py to library3)

CodePudding user response：

WARNING: This method is very hacky, and you might probably will break things.

Let's say we have this library1.py:

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

And, we want to overwrite it with overwrite.py:

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

If we go into a shell, we can see that a module has a __dict__ attribute that holds everything it has inside of it.

>>> 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}

This is nice, since we can use this to access the attributes without really accessing them:

>>> 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'

We don't want to overwrite any magic (starting and ending with two underscores) attributes, so:

>>> 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

We also don't want to overwrite any builtin functions:

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

>>> is_builtin(print)
True
>>> is_builtin(open)
True

This is where it all comes together.

We use values in library3 to overwrite the __dict__ of library1.

>>> 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

You can see that library1 has been overwritten:

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

CodePudding user response：

I found one way to do that:

import library1,library2,library3
import importlib

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

CodePudding user response：

You can use copy

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