How do I clear all variables in the middle of a Python script

Question

I am looking for something similar to  clear  in Matlab  A command function which removes all variables from the workspace  releasing them from system memory  Is there such a thing in Python   EDIT  I want to write a script which at some point clears all the variables

User · Answer

No  you are best off restarting the interpreter  IPython is an excellent replacement for the bundled interpreter and has the  reset command which usually works

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Isn t the easiest way to create a class contining all the needed variables   Then you have one object with all curretn variables  and if you need you can overwrite this variable

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The following sequence of commands does remove every name from the current module    gt  gt  gt  import sys  gt  gt  gt  sys modules   name      dict   clear     I doubt you actually DO want to do this  because  every name  includes all built-ins  so there s not much you can do after such a total wipe-out   Remember  in Python there is really no such thing as a  variable  -- there are objects  of many kinds  including modules  functions  class  numbers  strings        and there are names  bound to objects  what the sequence does is remove every name from a module  the corresponding objects go away if and only if every reference to them has just been removed    Maybe you want to be more selective  but it s hard to guess exactly what you mean unless you want to be more specific   But  just to give an example    gt  gt  gt  import sys  gt  gt  gt  this   sys modules   name     gt  gt  gt  for n in dir          if n 0        delattr this  n        gt  gt  gt    This sequence leaves alone names that are private or magical  including the   builtins   special name which houses all built-in names   So  built-ins still work -- for example    gt  gt  gt  dir       builtins        doc        name        package      n    gt  gt  gt     As you see  name n  the control variable in that for  also happens to stick around  as it s re-bound in the for clause every time through   so it might be better to name that control variable    for example  to clearly show  it s special   plus  in the interactive interpreter  name   is re-bound anyway after every complete expression entered at the prompt  to the value of that expression  so it won t stick around for long -    Anyway  once you have determined exactly what it is you want to do  it s not hard to define a function for the purpose and put it in your start-up file  if you want it only in interactive sessions  or site-customize file  if you want it in every script

User · Answer

In Spyder one can configure the IPython console for each Python file to clear all variables before each execution in the Menu Run - gt  Configuration - gt  General settings - gt  Remove all variables before execution

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The globals   function returns a dictionary  where keys are names of objects you can name  and values  by the way  are ids of these objects  The exec   function takes a string and executes it as if you just type it in a python console  So  the code is  for i in list globals   keys         if i 0                   exec  del     format i

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In the idle IDE there is Shell Restart Shell   Cntrl-F6 will do it

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from IPython import get ipython     get ipython   magic  reset -sf

User · Answer

If you write a function then once you leave it all names inside disappear   The concept is called namespace and it s so good  it made it into the Zen of Python      Namespaces are one honking great idea   -- let s do more of those    The namespace of IPython can likewise be reset with the magic command  reset -f   The -f means  force   in other words   don t ask me if I really want to delete all the variables  just do it

User · Answer

This is a modified version of Alex s answer  We can save the state of a module s namespace and restore it by using the following 2 methods       saved context         def saveContext        import sys       saved context   update sys modules   name      dict     def restoreContext        import sys     names   sys modules   name      dict   keys       for n in names          if n not in   saved context                del sys modules   name      dict   n   saveContext    hello    hi there  print hello               prints  hi there  on stdout  restoreContext    print hello               throws an exception   You can also add a line  clear   restoreContext  before calling saveContext   and clear   will work like matlab s clear

[python] How do I clear all variables in the middle of a Python script?

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