How to re import an updated package while in Python Interpreter

Question

I often test my module in the Python Interpreter  and when I see an error  I quickly update the  py file  But how do I make it reflect on the Interpreter   So  far I have been exiting and reentering the Interpreter because re importing the file again is not working for me

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dragonfly s answer worked for me  python 3 4 3    import sys del sys modules  module name     Here is a lower level solution    exec open  MyClass py   read    globals

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Not sure if this does all expected things  but you can do just like that    gt  gt  gt  del mymodule  gt  gt  gt  import mymodule

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No matter how many times you import a module  you ll get the same copy of the module from sys modules - which was loaded at first import mymodule  I am answering this late  as each of the above previous answer has a bit of the answer  so I am attempting to sum it all up in a single answer   Using built-in function   For Python 2 x - Use the built-in reload mymodule  function   For Python 3 x - Use the imp reload mymodule    For Python 3 4 - In Python 3 4 imp has been deprecated in favor of importlib i e  importlib reload mymodule   Few caveats     It is generally not very useful to reload built-in or dynamically loaded modules  Reloading sys    main    builtins and other key modules is not recommended   In many cases extension modules are not designed to be initialized more than once  and may fail in arbitrary ways when reloaded  If a module imports objects from another module using from     import      calling reload   for the other module does not redefine the objects imported from it     one way around this is to re-execute the from statement  another is to use import and qualified names  module name  instead   If a module instantiates instances of a class  reloading the module that defines the class does not affect the method definitions of the instances     they continue to use the old class definition  The same is true for derived classes      External packages   reimport - Reimport currently supports Python 2 4 through 2 7   xreload- This works by executing the module in a scratch namespace  and then patching classes  methods and functions in place   This avoids the need to patch instances   New objects are copied into the target namespace   livecoding - Code reloading allows a running application to change its behaviour in response to changes in the Python scripts it uses  When the library detects a Python script has been modified  it reloads that script and replaces the objects it had previously made available for use with newly reloaded versions  As a tool  it allows a programmer to avoid interruption to their workflow and a corresponding loss of focus  It enables them to remain in a state of flow  Where previously they might have needed to restart the application in order to put changed code into effect  those changes can be applied immediately

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Basically reload as in allyourcode s asnwer  But it won t change underlying the code of already instantiated object or referenced functions  Extending from his answer    Make a simple function that prints  version 1  shell1  echo  def x    print  version 1    gt  mymodule py    Run the module shell2  python  gt  gt  gt  import mymodule  gt  gt  gt  mymodule x   version 1  gt  gt  gt  x   mymodule x  gt  gt  gt  x   version 1  gt  gt  gt  x is mymodule x True     Change mymodule to print  version 2   without exiting the python REPL  shell2  echo  def x    print  version 2    gt  mymodule py    Back in that same python session  gt  gt  gt  reload mymodule   lt module  mymodule  from  mymodule pyc  gt   gt  gt  gt  mymodule x   version 2  gt  gt  gt  x   version 1  gt  gt  gt  x is mymodule x False

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So  far I have been exiting and reentering the Interpreter because re importing the file again is not working for me    Yes  just saying import again gives you the existing copy of the module from sys modules   You can say reload module  to update sys modules and get a new copy of that single module  but if any other modules have a reference to the original module or any object from the original module  they will keep their old references and Very Confusing Things will happen   So if you ve got a module a  which depends on module b  and b changes  you have to    reload b    followed by    reload a     If you ve got two modules which depend on each other  which is extremely common when those modules are part of the same package  you can t reload them both  if you reload p a it ll get a reference to the old p b  and vice versa  The only way to do it is to unload them both at once by deleting their items from sys modules  before importing them again  This is icky and has some practical pitfalls to do with modules entries being None as a failed-relative-import marker   And if you ve got a module which passes references to its objects to system modules     for example it registers a codec  or adds a warnings handler     you re stuck  you can t reload the system module without confusing the rest of the Python environment   In summary  for all but the simplest case of one self-contained module being loaded by one standalone script  reload   is very tricky to get right  if  as you imply  you are using a    package     you will probably be better off continuing to cycle the interpreter

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Short answer  try using reimport  a full featured reload for Python  Longer answer  It looks like this question was asked answered prior to the release of reimport  which bills itself as a  quot full featured reload for Python quot    This module intends to be a full featured replacement for Python s reload function  It is targeted towards making a reload that works for Python plugins and extensions used by longer running applications  Reimport currently supports Python 2 4 through 2 6  By its very nature  this is not a completely solvable problem  The goal of this module is to make the most common sorts of updates work well  It also allows individual modules and package to assist in the process  A more detailed description of what happens is on the overview page   Note  Although the reimport explicitly supports Python 2 4 through 2 6  I ve been trying it on 2 7 and it seems to work just fine

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Update for Python3   quoted from the already-answered answer  since the last edit comment here suggested a deprecated method      In Python 3  reload was moved to the imp module  In 3 4  imp was deprecated in favor of importlib  and reload was added to the latter  When targeting 3 or later  either reference the appropriate module when calling reload or import it    Takeaway    Python3    3 4  importlib reload packagename  Python3  lt  3 4  imp reload packagename  Python2  continue below     Use the reload builtin function   https   docs python org 2 library functions html reload     When reload module  is executed          Python modules    code is recompiled and the module-level code reexecuted  defining a new set of objects which are bound to names in the module   s dictionary  The init function of extension modules is not called a second time    As with all other objects in Python the old objects are only reclaimed after their reference counts drop to zero    The names in the module namespace are updated to point to any new or changed objects    Other references to the old objects  such as names external to the module  are not rebound to refer to the new objects and must be updated in each namespace where they occur if that is desired       Example     Make a simple function that prints  version 1  shell1  echo  def x    print  version 1    gt  mymodule py    Run the module shell2  python  gt  gt  gt  import mymodule  gt  gt  gt  mymodule x   version 1    Change mymodule to print  version 2   without exiting the python REPL  shell2  echo  def x    print  version 2    gt  mymodule py    Back in that same python session  gt  gt  gt  reload mymodule   lt module  mymodule  from  mymodule pyc  gt   gt  gt  gt  mymodule x   version 2

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In Python 3  the behaviour changes      gt  gt  gt  import my stuff       do something with my stuff  then later    gt  gt  gt  gt  import imp  gt  gt  gt  gt  imp reload my stuff    and you get a brand new  reloaded my stuff

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import sys del sys modules  module name

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All the answers above about reload   or imp reload   are deprecated   reload   is no longer a builtin function in python 3 and imp reload   is marked deprecated  see help imp     It s better to use importlib reload   instead

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See here for a good explanation of how your dependent modules won t be reloaded and the effects that can have   http   pyunit sourceforge net notes reloading html  The way pyunit solved it was to track dependent modules by overriding   import   then to delete each of them from sys modules and re-import   They probably could ve just reload ed them  though

[python] How to re import an updated package while in Python Interpreter?

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