Environmental preparation
Create a new foo folder with a bar.py file under it
$ tree foo
foo
└── bar.py
0 directories, 1 file
The content of bar.py is very simple, just write a print statement
print("successful to be imported")
As long as bar.py is imported once, a print is executed
Duplicate import is prohibited
Because of the existence of sys.modules, when you import an imported module, it actually has no effect.
>>> from foo import bar
successful to be imported
>>> from foo import bar
>>>
Repeat import method one
If you are using python2 (remember to add a __init__.py to the foo folder), there is a reload method that can be used directly
'''
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'''
>>> from foo import bar
successful to be imported
>>> from foo import bar
>>>
>>> reload(bar)
successful to be imported
<module 'foo.bar' from 'foo/bar.pyc'>
If you use python3, there are more methods, please see below for details
Repeat import method 2
If you use Python3.0 -> 3.3, then you can use imp.reload method
>>> from foo import bar
successful to be imported
>>> from foo import bar
>>>
>>> import imp
>>> imp.reload(bar)
successful to be imported
<module 'foo.bar' from '/Users/MING/Code/Python/foo/bar.py'>
But this method is deprecated in Python 3.4+
<stdin>:1: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
Repeat import method three
If you are using Python 3.4+, please use the importlib.reload method
'''
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'''
>>> from foo import bar
successful to be imported
>>> from foo import bar
>>>
>>> import importlib
>>> importlib.reload(bar)
successful to be imported
<module 'foo.bar' from '/Users/MING/Code/Python/foo/bar.py'>
Repeat import method five
Since it is sys.modules that affects our repeated import, can we just remove the imported package from it?
'''
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'''
>>> import foo.bar
successful to be imported
>>>
>>> import foo.bar
>>>
>>> import sys
>>> sys.modules['foo.bar']
<module 'foo.bar' from '/Users/MING/Code/Python/foo/bar.py'>
>>> del sys.modules['foo.bar']
>>>
>>> import foo.bar
successful to be imported